The psychological burden of peanut allergy as perceived by adults with peanut allergy and the parents of peanut-allergic children

Allergy-like conditions and health-care contacts among children with exclusion diets at school

AIM

To find out whether children with exclusion diet at school had allergy-like conditions that could explain their food avoidance, the objective of this study was to describe health-care contacts and diagnostic testing among schoolchildren with exclusion diet and compare the magnitude of allergy-like conditions between those children who had vs. had not consulted health-care professionals. Telephone interviews were conducted with the parents of 230 schoolchildren, aged 6-18 years, with certificates for exclusion diets at school.

RESULTS

The majority of the schoolchildren (85%) had consulted health-care professionals for food-related problems, and 68% were doctor-diagnosed as having food hypersensitivity. Those who had consulted health-care professionals specifically for their food-related problems had more complex and severe problems compared with those who had not consulted health-care professionals. Breathing difficulties (27/196) and anaphylaxis (9/196) related to intake of food were reported only for those who had sought health-care professionals (n = 196). Regardless of whether the children had consulted the health-care professionals, their food-related problems were consistent with food hypersensitivity. Schoolchildren avoided food items known to be associated with food hypersensitivity such as tree nuts, fruit, egg, peanut, lactose and fish. Furthermore, 83% of the 230 children also had allergic diseases (i.e. asthma, eczema or hay fever) or were hypersensitive to other substances besides food, and 83% had at least one sibling or parent with hypersensitivity to foods or other substances.

CONCLUSIONS AND IMPLICATIONS FOR THE SCHOOL NURSE

Schoolchildren with food certificates for exclusion diets, based on parents' statements, have food-related and allergy-like problems that may well motivate exclusion diets at school. The school nurses can rely on the parents' information as to what foods their children should avoid, even when doctor diagnoses have not been made or health-care consultations have not been carried out.

Gastrointestinal food allergy: new insights into pathophysiology and clinical perspectives

Adverse reactions to food that result in gastrointestinal symptoms are common in the general population; while only a minority of such individuals will have symptoms due to immunologic reactions to foods, gastrointestinal food allergies do exist in both children and adults. These immune reactions are mediated by immunoglobulin E-dependent and -independent mechanisms involving mast cells, eosinophils, and other immune cells, but the complexity of the underlying mechanisms of pathogenesis have yet to be fully defined. Knowledge of the spectrum of adverse reactions to foods that affect the digestive system, including gastrointestinal food allergy, is essential to correctly diagnose and manage the subset of patients with immunologically mediated adverse reactions to foods. Potentially fatal reactions to food necessitate careful instruction and monitoring on the part of health care workers involved in the care of individuals at risk of anaphylaxis. New methods of diagnosis and novel strategies for treatment, including immunologic modulation and the development of hypoallergenic foods, are exciting developments in the field of food allergy.

RETRACTED: Promising treatments in development for food allergies

Up to 6% of young children and 2% of adults suffer from food allergy. Among them many have IgE-mediated food allergy, a condition with potentially fatal allergic reactions. The only proven treatment is avoidance of the offending food, which can be identified using standardised allergic tests. However, several studies have addressed possible definite treatment options for food allergy. Immunotherapy, administered orally or by systemic injections, shows promising preliminary results, but these therapeutics are based on studies with insufficient scientific support, or are associated with a high risk of severe side effects. At present, no studies can support pharmacotherapy. However, promising results were recently published with anti-IgE antibodies in a human trial, and various approaches in a mouse model of food allergy (chinese herbal medicine, specific modulation of the T-cell response). Rapidly evolving findings might provide hope for a cure for food allergy in the near future.

Characterization of the T-cell epitopes of a major peanut allergen, Ara h 2

BACKGROUND

The development of safe and effective immunotherapy for peanut allergy has been complicated by the high anaphylactic potential of native peanut extracts. We sought to map the T-cell epitopes of the major peanut allergen, Ara h 2 in order to develop T-cell targeted vaccines.

METHODS

A panel of eight peanut-specific CD4+ T-cell lines (TCL) was derived from eight peanut-allergic subjects and proliferative and cytokine responses to stimulation with a set of overlapping 20-mer peptides representing the entire sequence of Ara h 2 determined. Proliferation was assessed in 72 h assays via tritiated thymidine incorporation, while interleukin (IL)-5 and interferon (IFN)-gamma production were assessed via sandwich enzyme-linked immunosorbent assay (ELISA) of cell culture supernatants.

RESULTS

Eight of the 17 Ara h 2 peptides were recognized by one or more subjects, with the two peptides showing highest reactivity [Ara h 2 (19-38) and Ara h 2 (73-92)] being recognized by three subjects each. Adjoining peptides Ara h 2 (28-47) and Ara h 2 (100-119) induced proliferative responses in two subjects. Each of these peptides was associated with a Th2-type cytokine response.

CONCLUSION

Two highly immunogenic T-cell reactive regions of Ara h 2 have been identified, Ara h 2 (19-47) and Ara h 2 (73-119), providing scope for the development of safe forms of immunotherapy for peanut allergy.

Health-related quality of life among adolescents with allergy-like conditions - with emphasis on food hypersensitivity

BACKGROUND

It is known that there is an increase in the prevalence of allergy and that allergic diseases have a negative impact on individuals' health-related quality of life (HRQL). However, research in this field is mainly focused on individuals with verified allergy, i.e. leaving out those with self-reported allergy-like conditions but with no doctor-diagnosis. Furthermore, studies on food hypersensitivity and quality of life are scarce. In order to receive information about the extent to which adolescent females and males experience allergy-like conditions and the impact of these conditions on their everyday life, the present study aimed to investigate the magnitude of self-reported allergy-like conditions in adolescence and to evaluate their HRQL. Special focus was put on food hypersensitivity as a specific allergy-like condition and on gender differences.

METHODS

In connection with lessons completed at the children's school, a study-specific questionnaire and the generic instrument SF-36 were distributed to 1488 adolescents, 13-21 years old (response rate 97%).

RESULTS

Sixty-four per cent of the respondents reported some kind of allergy-like condition: 46% reported hypersensitivity to defined substances and 51% reported allergic diseases (i.e. asthma/wheezing, eczema/rash, rhino-conjunctivitis). A total of 19% reported food hypersensitivity. Females more often reported allergy-like conditions compared with males (p < 0.001). The adolescents with allergy-like conditions reported significantly lower HRQL (p < 0.001) in seven of the eight SF-36 health scales compared with adolescents without such conditions, regardless of whether the condition had been doctor-diagnosed or not. Most adolescents suffered from complex allergy-like conditions.

CONCLUSIONS

The results indicate a need to consider the psychosocial impact of allergy-like conditions during school age. Further research is needed to elucidate the gender differences in this area. A team approach addressing better understanding of how allergy-like conditions impair the HRQL may improve the management of the adolescent's health problems, both in health-care services and in schools.

Food allergy in young adults: perceptions and psychological effects

Although food allergy can have serious health consequences, little is currently known about people's perceptions of food allergy. The present study examined the differences in awareness and perceptions of food allergy and anxiety between young people with and without a food allergy. Participants completed a questionnaire which asked about their perceptions and knowledge of allergies, perceived health competence and anxiety. Of the 162 participants 24 reported they were allergic to at least one food; these people perceived that their allergy had significantly less of an impact on their lives than others believed it would. Allergy status interacted with perceived health competence to affect anxiety. People with an allergy and with high health competence reported the greatest anxiety levels. Very few of the sample knew the meaning of the term 'anaphylaxis'. Findings are discussed in terms of health education implications and possibilities.

Specific immunoglobulin E antibodies to peanut over time in relation to peanut intake, symptoms and age

The clinical outcome of peanut allergy and some factors associated with development of peanut allergy remain unsolved. It has not been clarified to what extent peanut intake affects immunoglobulin (IgE) antibody formation in peanut sensitized individuals. The aim of the study was to investigate the development of peanut hypersensitivity in children and adolescents with specific IgE antibodies to peanut, using questionnaires and current serum tests and comparing it to information obtained 5-6 yr earlier, to investigate how peanut intake during this period related to subject age, IgE antibody levels and symptoms and to investigate what information this patient group was given at the time of diagnosis regarding avoidance of peanut related food. All patients with detectable peanut-specific IgE antibodies investigated during 1994-1996 deriving from two allergy laboratories in the western region of Sweden were traced and reinvestigated (n=132). A total of 111 subjects (63 with peanut allergy and 48 peanut sensitized) participated in the questionnaire. Eighty-six of them consented to be enrolled in a further interview and renewed testing of specific IgE antibody to peanut 5 yr later. All tests were done using the Pharmacia CAP system. Increased IgE antibody levels during follow-up was related to age; subjects 0-6 yr at initial test occasion were more likely to have higher IgE antibody class than the older individuals (p=0.018). Exposure to peanut during the study, i.e. 5-6 yr since diagnosis, did not seem to affect the result. During the follow-up period, 29 out of 86 (34%) increased their IgE antibody class. At the second test occasion the remaining subjects had similar (28%) or lowered (38%) levels of IgE antibodies. Exposure to peanut during follow-up was more common in subjects with IgE antibody class 1-3 compared to subjects with high value (> 3) at the initial test (p=0.003). Reported symptoms during follow-up were also more common in subjects with initially high IgE antibody value. Individuals with initially high IgE antibodies to peanut had been given more information about peanut allergy and cross-reacting allergens than other individuals. The subjects over 6 yr of age showed a decrease in peanut-specific IgE class over a 5-yr period. Together with the literature, our result suggest that follow-up and renewed testing is recommended, since there may be a change in IgE antibody classes and clinical sensitivity over time. Even in Sweden, with a low consumption of peanuts, the youngest individuals with peanut sensitization experienced a similar course of events that has been reported in other countries.

General paediatricians and the case of resolving peanut allergy

Children with peanut allergy are almost always advised to avoid nuts for life. There have been recent reports from academic centres that in some cases the allergy might resolve and thus these dietary restrictions can be lifted. To evaluate resolution of peanut allergy in a selected group of children in a general paediatric setting. Children 4-16 yr old with a clear history of an allergic reaction to peanuts who had not had any reaction in the previous 2 yr were eligible. Specific immunoglobulin E (IgE) or skin prick test (SPT) at the time of diagnosis was sought. A SPT and specific IgE was then done and if this was <or= 8 mm and <or= 17.5 kU[A]/l respectively, a double-blind placebo-controlled food challenge was undertaken. A negative challenge consisted of tolerance to a cumulative dose of 15.8 g peanuts followed by an open challenge. From the 82 case notes reviewed 54 children were eligible to participate. Twenty-nine agreed to participate and underwent SPT (29) and specific IgE (28). Of these children eight were eligible for food challenge. Four challenges were negative and four positive. Peanut allergy may resolve in approximately 15% of selected children attending an allergy clinic run by general paediatricians in a district general hospital. Food challenge constitutes the appropriate way of removing the burden that comes with a diagnosis of peanut allergy and enables dietary restriction to cease.

Monitoring of IgE-mediated food allergy in childhood

BACKGROUND

The prevalence of IgE-mediated food allergy (FA) in childhood varies from 6% to 8% in the first year of life compared to 1% to 2% in adults. In contrast to adults, FA in childhood, often part of the "allergic march", resolves in more than 85% of children, especially those with hypersensitivity to cow's milk and egg.

AIM

This paper explains the rationale for continuing care for childhood FA and describes how children should be monitored for resolution/persistence of FA.

METHODS

A clinical, multidisciplinary approach and management algorithm based on relevant, peer-reviewed original research articles and reviews using the keywords anaphylaxis, atopic eczema, children, milk allergy, double-blind placebo-controlled food challenge, egg allergy, epinephrine, failure to thrive, food allergy, food challenge, food hypersensitivity, immunoglobulin E, nutrition, natural history, paediatrics, peanut allergy, prevalence, psychosocial factors, quality of life, radioallergosorbent test, and tolerance from years 1966 to 2003 in MEDLINE. Additional studies were identified from article reference lists.

RESULTS

A combination of outcome measures, a multidisciplinary approach involving a dietitian and allergy nurse specialist, and a management algorithm are useful tools in clinical management.

CONCLUSIONS

Prospective studies of non-selected children, optimally from birth cohorts, are needed to evaluate the effects of such management programmes regarding FA in childhood.

Influence of a multidisciplinary paediatric allergy clinic on parental knowledge and rate of subsequent allergic reactions

BACKGROUND

Studies have demonstrated that families of children with food allergy have significant deficiencies in their knowledge of how to avoid allergen exposure and how to manage allergic reactions. This study aims to assess the impact of a multidisciplinary paediatric allergy clinic consultation on parental knowledge of food allergy and to determine the rate of subsequent allergic reactions.

METHODS

Sixty-two subjects (<17 years) referred with food allergy were prospectively enrolled. Parental knowledge was assessed by questionnaire and EpiPen trainer. Families saw a paediatric allergist, clinical nurse specialist and dietician. Knowledge was reassessed after 3 months and rate of allergic reactions after 1 year.

RESULTS

After one visit to the paediatric allergy clinic, there was a significant improvement in parental knowledge of allergen avoidance (26.9%, P < 0.001), managing allergic reactions (185.4%, P < 0.0001) and EpiPen usage (83.3%, P < 0.001). Additionally, there was a significant reduction in allergic reactions (P < 0.001). Children with egg, milk or multiple food allergies were more likely to suffer subsequent reactions.

CONCLUSIONS

A single visit to a multidisciplinary allergy clinic considerably improves families' abilities to manage allergic reactions to foods with an accompanying reduction in allergic reactions. Young children with egg, milk or multiple food allergies were at greatest risk of further reactions.

Assessment of quality of life in children with peanut allergy

Children with a peanut allergy (PA) are faced with food and social restrictions due to the potentially life-threatening nature of their disease, for which there is no cure or treatment. This inevitably impacts upon their quality of life (QoL). QoL of 20 children with PA and 20 children with insulin-dependent diabetes mellitus (IDDM) was measured using two disease-specific QoL questionnaires (higher scores correspond to a poorer QoL). One questionnaire was designed by us and the other was adapted from the Vespid Allergy QoL questionnaire. We gave subjects cameras to record how their QoL is affected over a 24-h period. Response rates for both questionnaires were 100%. Mean ages were 9.0 and 10.4 years for PA and IDDM subjects, respectively. Children with a PA reported a poorer quality of life than children with IDDM: mean scores were 54.85 for PA subjects and 46.40 for diabetics (p = 0.004) in questionnaire 1 and 54.30 and 34.50 (p</=0.001) in questionnaire 2. PA children reported more fear of an adverse event and more anxiety about eating, especially when eating away from home. Photographs fell into seven common categories: food, management, environment, away from home, physical activities, restaurant and people. Most photographs related to food and management issues and revealed difficulties for both groups regarding food restrictions. PA subjects felt more threatened by potential hazards within their environment, felt more restricted by their PA regarding physical activities, and worried more about being away from home. However, they felt safe when carrying epinephrine kits and were positive about eating at familiar restaurants. The QoL in children with PA is more impaired than in children with IDDM. Their anxiety may be considered useful in some situations, promoting better adherence to allergen avoidance advice and rescue plans.

Anaphylaxis: risk factors for recurrence

BACKGROUND

There are few studies on the incidence or recurrence of anaphylaxis.

OBJECTIVE

To examine the incidence of anaphylaxis and risk factors for recurrence.

METHODS

A prospective study of 432 patients referred to a community-based specialist practice in the Australian Capital Territory with anaphylaxis, followed by a survey to obtain information on recurrence.

RESULTS

Of 432 patients (48% male, 73% atopic, mean 27.4 years, SD 19.5, median 26) with anaphylaxis, 260 patients were seen after their first episode; 172 experienced 584 previous reactions. fifty-four percent of index episodes were treated in hospital. Aetiology was identified in 91.6% patients: food (61%), stinging insects (20.4%) or medication (8.3%). The minimum occurrence and incidence of new cases of anaphylaxis was estimated at 12.6 and 9.9 episodes/100,000 patient-years, respectively. Follow-up data were obtained from 304 patients (674 patient-years). One hundred and thirty experienced further symptoms (45 serious), 35 required hospitalization and 19 administered adrenaline. Accidental ingestion of peanut/tree nut caused the largest number of relapses, but the highest risk of recurrence was associated with sensitivity to wheat and/or exercise. Rates of overall and serious recurrence were 57 and 10 episodes/100 patient-years, respectively. Of those prescribed adrenaline, 3/4 carried it, 2/3 were in date, and only 1/2 patients faced with serious symptoms administered adrenaline. Five patients each developed new triggers for anaphylaxis, or re-presented with significant psychiatric symptoms.

CONCLUSION

In any 1 year, 1/12 patients who have suffered anaphylaxis will experience recurrence, and 1/50 will require hospital treatment or use adrenaline. Compliance with carrying and using adrenaline is poor. Occasional patients develop new triggers or suffer psychiatric morbidity.

Management of food allergies

Worldwide, approximately 8 and 2% of children and adults, respectively, suffer from food allergy. Cow's milk, egg, peanut, soy, wheat, fish, shellfish and tree nuts are responsible for the majority of allergic reactions to foods. Allergic reactions to food can occur by a variety of immune mechanisms including: IgE-mediated; non-IgE-mediated (T-cell-mediated); and combined IgE- and T-cell-mediated. Food allergies can affect any organ system, but most frequently involve the gastrointestinal system, the skin and the respiratory system. Knowledge of the spectrum of food allergies is important in order to identify patients at risk for severe or life-threatening allergic reactions. This article will review the mechanisms of specific food allergy disorders. It will also summarise the diagnosis of food allergy including the history of a food reaction, skin tests and laboratory tests. The management of food allergy will also be discussed with particular emphasis on the avoidance of food allergens and the pharmacotherapy of allergic reactions. Future therapy for food allergies will also be discussed.

The predictive value of a positive prick skin test to peanut in atopic, peanut-naïve children

BACKGROUND

Although allergy testing before food ingestion is generally not recommended, many peanut-naive children undergo prick skin tests (PSTs) to peanut because of atopy. Children with positive PSTs are generally advised to avoid peanuts either indefinitely or until a definitive diagnosis is made through challenge.

OBJECTIVE

To describe peanut challenges in atopic, peanut-naive children with PST to peanuts > or = 3 mm and the PST properties in this population.

METHODS

Between 1994 and 2001, 47 patients were identified who had a positive peanut PST, no previous peanut ingestion, and had undergone a peanut challenge.

RESULTS

Forty-nine percent of the challenges were positive. The mean of the largest wheal diameter (95% confidence interval [CI]) of the PST in children having a negative and positive challenge was 6.3 mm (CI, 5.3 to 7.3) and 10.3 mm (CI, 8.9 to 11.8), respectively. At a PST cutoff of > or = 5 mm, the sensitivity and negative predictive value (95% CI) was 100% (85.2 to 100) and 100% (29.2 to 100), whereas the specificity and positive predictive value (95% CI) was 12.5% (2.7 to 32.4) and 52.3% (36.7 to 67.5), respectively.

CONCLUSIONS

We show that 49% of atopic, peanut-naïve children sensitized to peanut developed allergic symptoms during oral provocation with peanut. Although the sensitivity of the PST at > or = 5 mm for the detection of peanut allergy in this study was 100%, our small sample size limits the applicability of this value. Further investigation is needed to determine whether children with wheal diameters of 3 or 4 mm, perhaps coupled with low peanut-specific IgE, could undergo less resource-intensive, accelerated challenges.

Engineered recombinant peanut protein and heat-killed Listeria monocytogenes coadministration protects against peanut-induced anaphylaxis in a murine model

Peanut allergy (PNA) is the major cause of fatal and near-fatal anaphylactic reactions to foods. Traditional immunotherapy using peanut (PN) protein is not an option for PNA therapy because of the high incidence of adverse reactions. We investigated the effects of s.c. injections of engineered (modified) recombinant PN proteins and heat-killed Listeria monocytogenes (HKLM) as an adjuvant on anaphylactic reactions in a mouse model of PN allergy. PN-allergic C3H/HeJ mice were treated s.c. with a mixture of the three major PN allergens and HKLM (modified (m)Ara h 1-3 plus HKLM). The effects on anaphylactic reactions following PN challenge and the association with Ab levels and cytokine profiles were determined. Although all mice in the sham-treated groups exhibited anaphylactic symptoms with a median symptom score of 3, only 31% of mice in the mAra h 1-3 plus HKLM group developed mild anaphylaxis, with a low median symptom score of 0.5. Alterations in core body temperature, bronchial constriction, plasma histamine, and PN-specific IgE levels were all significantly reduced. This protective effect was markedly more potent than in the mAra h 1-3 protein alone-treated group. HKLM alone did not have any protective effect. Reduced IL-5 and IL-13, and increased IFN-gamma levels were observed only in splenocytes cultures from mAra h 1-3 plus HKLM-treated mice. These results show that immunotherapy with modified PN proteins and HKLM is effective for treating PN allergy in this model, and may be a potential approach for treating PNA.

Food allergy: an overview

Food allergy affects between 5% and 7.5% of children and between 1% and 2% of adults. The greater prevalence of food allergy in children reflects both the increased predisposition of children to develop food allergies and the development of immunologic tolerance to certain foods over time. Immunoglobulin (Ig) E-mediated food allergies can be classified as those that persist indefinitely and those that are predominantly transient. Although there is overlap between the two groups, certain foods are more likely than others to be tolerated in late childhood and adulthood. The diagnosis of food allergy rests with the detection of food-specific IgE in the context of a convincing history of type I hypersensitivity-mediated symptoms after ingestion of the suspected food or by eliciting IgE-mediated symptoms after controlled administration of the suspected food. Presently, the only available treatment of food allergies is dietary vigilance and administration of self-injectable epinephrine.

Psychological aspects of food allergy

Food allergies may impact the emotions of patients through both direct and indirect mechanisms. Direct mechanisms include the effects on the central nervous system from biologic mediators released during an allergic reaction to food. Indirect mechanisms include the stress of coping with a food allergy--for example, food preparation and avoidance--as well as managing the fear of the potential consequences of ingesting the food. Indirect effects may also be mediated through family members--for example, the impact of a parent's stress on the child. These relationships are difficult to study, in part because many patients who report food allergy symptoms do not have objective symptoms when challenged with the offending food. Symptoms may be misinterpreted as food allergy more often by patients with certain psychological profiles. In this paper, relevant literature is reviewed, and clinical treatment designed to minimize the emotional suffering of patients and their families is presented through the description of a case vignette.

Rising prevalence of allergy to peanut in children: Data from 2 sequential cohorts

BACKGROUND

Allergy to peanut is common. However, it is not known whether the prevalence of sensitization and clinical allergy to peanut is increasing.

OBJECTIVE

We sought to determine any change in the prevalence of peanut sensitization and reactivity in early childhood in 2 sequential cohorts in the same geographic area 6 years apart.

METHODS

Of 2878 children born between September 1, 1994, and August 31, 1996, living on the Isle of Wight, 1273 completed questionnaires, and 1246 had skin prick tests at the age of 3 to 4 years. Those with positive skin prick test responses to peanut were subjected to oral peanut challenges, unless there was a history of immediate systemic reaction. These data were compared with information on sensitization and clinical allergy to peanut available from a previous cohort born in 1989 in the same geographic area.

RESULTS

There was a 2-fold increase in reported peanut allergy (0.5 % [6/1218] to 1.0 % [13/1273]), but the difference was nonsignificant (P =.2). Peanut sensitization increased 3-fold, with 41 (3.3 %) of 1246 children sensitized in 1994 to 1996 compared with 11 (1.1 %) of 981 sensitized 6 years ago (P =.001). Of 41 sensitized children in the current study, 10 reported a convincing clinical reaction to peanut, and 8 had positive oral challenge results, giving an overall estimate of peanut allergy of 1.5% (18/1246).

CONCLUSIONS

Sensitization to peanut had increased between 1989 and 1994 to 1996. There was a strong but statistically nonsignificant trend for increase in reported peanut allergy.

Improved screening for peanut allergy by the combined use of skin prick tests and specific IgE assays

BACKGROUND

The diagnosis of peanut allergy must be based on reliable, safe criteria. Double-blind, placebo-controlled food challenges (DBPCFCs) are the gold standard but are costly and dangerous because they can trigger severe reactions.

OBJECTIVE

The aim of this study was to develop a new strategy for diagnosing peanut allergy while reducing the need for DBPCFCs.

METHODS

We studied 363 children referred for an evaluation of suspected food hypersensitivity. They all benefited from the same diagnostic strategy, which included, in order, clinical history, a skin prick test (SPT), and a specific IgE assay. DBPCFCs were performed on all the children by personnel who were unaware of the results of the other tests. To assess the performance characteristics of the SPT (comparing commercial and raw peanut extracts) and the specific IgE assay, we compared the results with those provided by the DBPCFCs. For SPTs and specific IgE assays, we sought to determine the cutoff values required to exclude false-positive and false-negative results.

RESULTS

According to DBPCFC results, 177 children were allergic to peanut, and 186 were not. The performance characteristics of the SPTs were superior with the raw extract because the negative predictive value was 100% (95% confidence interval [CI], 97.5-100). If the skin reaction with the raw extract was less than 3 mm, we could be quite certain that the child was not allergic. On the other hand, if the SPT resulted in a wheal diameter of larger than 3 mm, we could only be 74% certain that the children were allergic. Furthermore, if the SPT resulted in a wheal diameter of 16 mm or larger, we could be quite certain that the child was allergic because the positive predictive value was 100% (95% CI, 86.8-100). Specific IgE concentrations of 57 kU(A)/L or greater were associated with a positive predictive value of 100% (95% CI, 87.2-100). The combined use of the tests resulting in a positive diagnosis if the SPT result was 16 mm or larger or specific IgE concentration was 57 kU(A)/L or greater and in a negative diagnosis if the SPT result was less than 3 mm and the specific IgE concentration was less than 57 kU(A)/L allowed us to classify subjects with almost complete certainty as being allergic or not because the predictive values were 100%.

CONCLUSION

Commercial extracts could not be used to reliably predict tolerance of peanut. Peanut DBPCFCs can be avoided when SPTs with raw extracts resulted in wheals with a largest diameter of less than 3 mm and a specific IgE concentration of less than 57 kU(A)/L and also when wheal diameters were 16 mm or larger or specific IgE values were 57 kU(A)/L or greater. Otherwise, DBPCFCs were indispensable for the unequivocal diagnosis of peanut allergy.

Clinical update on peanut allergy

BACKGROUND

Peanut allergy is common, potentially severe, and there has been a recent surge in clinical investigation of this important food allergen.

OBJECTIVE

To provide the reader with a clinically oriented update on peanut allergy.

DATA SOURCES

English language articles were selected from PubMed searches (search terms: peanut allergy, food allergy, anaphylaxis) and selected abstracts with a bias toward recent (3 years) studies judged to have immediate, practical clinical implications.

RESULTS

Peanut allergy is an increasing problem in western diets that include this food. Both genetic and environmental factors influences the expression of this allergy. The at-risk subject is an atopic individual, with heightened risk for those with atopic dermatitis and/or other food allergies. The allergy is long-lived for most, may increase slightly in severity over time, but approximately 20% of young children will develop tolerance. Parameters that may identify the subset likely to achieve tolerance have been identified. Several large studies have determined laboratory parameters (skin tests, peanut-specific serum immunoglobulin E concentrations) with excellent predictive value (>95%) to diagnose current clinical reactivity or tolerance, although oral food challenges are necessary for a definitive diagnosis. Numerous practical lessons concerning management (avoidance, treatment, and prevention) have been identified.

CONCLUSIONS

Recent studies provide the clinician with an armament of improved diagnostic and treatment modalities for peanut allergy. Studies are underway that are likely to provide more definitive therapies in the near future.

Food allergen avoidance: risk assessment for life

The skills and knowledge required to carry out food allergen avoidance are becoming increasingly sophisticated. It is not enough to know the names of a handful of dishes which contain a known allergen as an ingredient. Many lifestyles now depend on food prepared away from the home. New product development has introduced a wide range of ingredients and dishes which are labour saving, exciting and innovative. Product traceability now depends on advanced technological support as it struggles to keep up with foods manufactured, prepared and served in ever more complex circumstances. Consumers are now faced with 'a jungle of choices'. However, those individuals who need to avoid a known allergen, particularly in trace quantities, often find that the food choice deemed suitable is poor, and the information available inadequate or even dangerously misleading. There are two important groups for whom this situation is a major concern. Thousands of families with young children are forced to live with the possibility that everyday foods may be contaminated by a known allergen which could kill in minutes. They live on their nerves, reading every packet and resorting to hyperprotective childcare and vigilance. In addition, the youngest independent consumers, teenagers and those in their twenties, may have little first-hand experience of food preparation. They may be ill-equipped in food-allergen risk assessment. Sadly, those who die from anaphylaxis or allergen-triggered asthma are often in this age-group. Current initiatives to support consumers at risk include a recognised standard for manufacturers seeking to eliminate an allergen from their production, and the integration of food allergy into training for caterers and food standards enforcement professionals.

Food allergy in children

Food allergies are increasing in prevalence and as a disease burden throughout the world, however they seem to increasingly affect countries with a formerly low prevalence. Consideration and diagnosis of food allergies are important as it has ramifications that affect a child's diet, care at school and home and is recognised to be associated with anxiety of parents, family and care takers. Food allergies vary significantly between countries, however nut allergies appear to be widely associated with serious reactions and death. The value of specific food immunoglobulin E (IgE) and skin prick tests (SPT) has been extensively analysed in children in recent years and can provide very useful information in an appropriately selected population. Diagnosis may require formal challenges to confirm a genuine allergic reaction condition rather than an intolerance reaction due to other mechanisms. The medical care of a food allergic child requires concurrent dietary advice and management, risk avoidance and emergency management plans. Reintroduction of foods occurs when the risk profile is appropriate based mainly on the predictive information obtained by SPTs and specific IgE levels. Fortunately allergies to egg and milk resolve by 3-5 years in about 80% of children. There have been some recent advances in immunotherapeutic approaches to food allergy although this has not translated to success in human treatment to date.

Natural history of peanut allergy

Peanut allergy raises major concerns and requires diligence in families because of the possibility of severe reactions, the perceived inability to outgrow peanut allergy, and the widespread availability of peanuts in the Western diet. However, studies in the past year have shown that a subset of patients with peanut allergy can become tolerant to peanut. The patients with the milder reactions on presentation have a better chance to develop tolerance to peanuts than the patients whose first reaction is anaphylaxis. This review will focus on the mechanism of allergic sensitization to peanuts and the natural history of peanut allergy as it is currently evolving. The effects of cooking and altering peanut allergens are discussed as are potential treatment modalities.

The impact of childhood food allergy on quality of life

BACKGROUND

Food allergy affects >6% of children, but the impact of this disease on health-related quality of life has not been well studied.

METHODS

Parental perceptions of physical and psychosocial functioning were measured with the Children's Health Questionnaire (CHQ-PF50). This tool and an additional allergy-related questionnaire were sent to 400 members of the Food Allergy and Anaphylaxis Network with children aged 5 to 18, an age group on which the tool has been validated.

RESULTS

Surveys were completed by 253 parents (63%). The mean age of the food-allergic children was 10.8 years (range, 5 to 18 yrs); 59% were male. Sixty-eight percent were allergic to one or two foods, the remainder to more than two foods. Concomitant chronic atopic diseases included: asthma with atopic dermatitis (33%), atopic dermatitis alone (13%), asthma alone (33%), and 21% had neither asthma nor atopic dermatitis. In comparison to previously established norms, the families scored significantly lower (more than 10 scale score points lower and P < 0.0001) for general health perception (GH), emotional impact on the parent (PE), and limitation on family activities (FA). Associated atopic disease, influenced primarily by those with both asthma and atopic dermatitis, accounted for a significant reduction in the GH scale (analysis of variance, P = 0.0001), but not for measures of PE and FA. Within the study group, food-allergic individuals with several (more than two) food allergies had significantly lower (P < 0.05) scores for 7 of 12 scales compared with individuals with few (one or two) food allergies. However, those with one or two food allergies scored significantly lower (P < 0.0001) than established norms on scales for GH, PE, and FA.

CONCLUSIONS

Childhood food allergy has a significant impact on GH, PE, and FA. Factors that influence reductions in these scales include associated atopic disease and the number of foods being avoided.

Food allergen avoidance--the patient's viewpoint

The profile of potentially fatal food allergies has altered in recent years. The vigilance required for allergen avoidance when shopping or eating out depends on information which is often hidden or misleading. Families with allergic children suffer social exclusion and stress, made worse by a serious shortage of specialist patient care. Those who die are usually teenagers and young adults who suffer from severe allergic asthma or anaphylaxis after eating away from the home. A recognised manufacturing standard would endorse businesses seeking to remove the risk of allergen cross-contamination, whilst the integration of allergy into training for caterers and environmental health professionals would influence and inform foodservice businesses.

The threshold concept in food safety and its applicability to food allergy

Down the years there have been many clinical reports of exquisite sensitivity to low doses of food allergens. There are many factors that may contribute to a variation of threshold in an individual exposed to an allergen during the course of his or her daily life. Some of these factors are intrinsic and unavoidable. Other factors may be predictable but not easily controllable, such as asthma, exposure to allergens during the pollen season and predicting situations that may be risky. Other factors may be out of the control of the individual. The most important one of these is the adequate training and awareness of manufacturers and caterers who aim to provide safe and nutritious meals to their allergic and non-allergic customers alike. Clinical histories of reactions in the community and the use of labial exposure during food challenge show that most non-ingestion exposures to peanut usually result in easily treated minor reactions. Formal, oral food challenges have shown that low dose reactivity is relatively common but studies have not yet had the power to investigate whether peanut allergy is more commonly associated with very low dose reactivity than other foods. This means that industry must not concentrate only on peanut and tree nuts when looking at issues of contamination just because they are associated with the majority of severe reactions. There are more milk and egg allergic children in the general population and they deserve the same protection from allergen exposure as sufferers of peanut or tree nut allergies.

Risk assessment for food allergy--the industry viewpoint

A safe food supply is a legitimate expectation of consumers, which the food industry must meet. Allergic reactions to food are recognised as a significant public health problem. Protecting allergic consumers against such reactions, while minimising the impact of food allergy on their quality of life, poses a challenge to the industry. Risk assessment is the process whereby the likelihood of an adverse event is related to exposure. Allergic reactions to foods can arise in one of three ways, which are not mutually exclusive. Firstly, a known allergen may be present in a food at a level above that at which the allergic individual reacts, secondly, an individual may react to a known or novel allergen because of sensitisation to another, cross-reactive, allergen and finally sensitisation may occur to a novel allergen, followed by reaction on subsequent exposure. A total absence of risk of reaction to an allergen implies no exposure, a situation which in most food manufacturing environments is unrealistic, and in any event would not help in the context of novel allergens. Possible approaches to risk assessment for food allergy in each of the contexts described above are examined, together with their limitations.

Peanut challenge: a retrospective study of 140 patients

BACKGROUND

Accurate diagnosis of peanut allergy is essential given that it is a lifelong and potentially fatal food allergy. Diagnosis relies on patient history, prick skin test (PST), and in many situations, food challenge. More information is required on the safety of food challenge and the informational value of a PST.

OBJECTIVES

Primary: to assess the safety of peanut challenges. Secondary: to estimate the sensitivity, specificity, and the positive and negative predictive values of PST to peanut performed in those who underwent a peanut challenge.

METHODS

A retrospective study of peanut challenges performed at a tertiary care paediatric hospital allergy clinic between January 1994 and November 1998.

RESULTS

Of the 140 peanut challenges performed on 140 patients, 18 were positive. The most frequent adverse clinical effects of positive peanut challenges were: urticaria, oropharyngeal irritation, rhinitis, vomiting and abdominal pain. Among the 18 patients who had a positive result, 10 required medical treatment (antihistamines, +/- epinephrine, +/- salbutamol) to control the allergic reaction. The sensitivity, specificity, and the positive and negative predictive values of PST to peanut in this group of children undergoing a peanut challenge were 100%, 62.3%, 28.1% and 100%, respectively.

CONCLUSIONS

Given the poor positive predictive value and specificity of PST, a peanut challenge is usually required to diagnose peanut allergy with certainty when the PST is positive. In cases of a clear history of anaphylaxis to peanut and a positive PST, challenges are unwarranted. When the history is strongly suggestive and the PST is borderline positive, i.e. 3 or 4 mm, peanut challenge is generally necessary to confirm the diagnosis. Given the excellent negative predictive value and sensitivity of PST, a blinded peanut challenge is usually unnecessary in the context of a negative PST except for patients with a history strongly suggestive of immediate hypersensitivity. These patients should be individually assessed for the need to undergo a blinded challenge. The peanut challenge is a useful and safe diagnostic tool when performed by qualified personnel under appropriate conditions.

Diagnosis and management of food allergy

Food allergy affects 8% of children under 3 years of age and roughly 2% of the adult population. Major targets include cutaneous, gastrointestinal, and respiratory organs. Clinicians must recognize the spectrum of food allergy in order for these patients to be diagnosed accurately and managed. IgE-mediated reactions can progress rapidly, and severe reactions are often associated with refractory bronchoconstriction. IgE-mediated allergic patients should be equipped with education, an emergency action plan, and injectable epinephrine to aggressively treat food-induced reactions and prevent fatalities.