Food sensitivity and the pathogenesis of atopic dermatitis

Drug-induced skin toxicity: gaps in preclinical testing cascade as opportunities for complex in vitro models and assays

Skin is the largest organ of the body and serves as the principle barrier to the environment. Composed of multiple cell types arranged in stratified layers with highly specialized appendages, it serves sensory and immune surveillance roles in addition to its primary mechanical function. Several complex in vitro models of skin (i.e. microphysiological systems (MPS) including but not limited to 3D tissues, organ-on-a-chip, organoids), have been developed and assays validated for regulatory purposes. As such, skin is arguably the most advanced organ with respect to model development and adoption across industries including chemical, cosmetic, and to a somewhat lesser extent, pharmaceutical. Early adoption of complex skin models and associated assays for assessment of irritation and corrosion spurred research into other areas such as sensitization, absorption, phototoxicity, and genotoxicity. Despite such considerable advancements, opportunities remain for immune capabilities, inclusion of appendages such as hair follicles, fluidics, and innervation, among others. Herein, we provide an overview of current complex skin model capabilities and limitations within the drug development scheme, and recommendations for future model development and assay qualification and/or validation with the intent to facilitate wider adoption of use within the pharmaceutical industry.

Are avoidance diets still warranted in children with atopic dermatitis?

Nearly 40% of children with moderate-to-severe atopic dermatitis (AD) have IgE-mediated food allergy (FA). This clinical observation has been extensively documented by experimental data linking skin inflammation in AD to FA, as well as by food challenges reproducing symptoms and avoidance diets improving AD. Although food avoidance may improve AD, avoidance diets do not cure AD, may even have detrimental effects such as progression to immediate-type allergy including anaphylactic reactions, and may significantly reduce the quality of life of the patient and the family. AD care should focus upon optimal medical management, rather than dietary elimination. Food allergy testing is primarily indicated when immediate-type allergic reactions are a concern. In recalcitrant AD, if food is being considered a possible chronic trigger, a limited panel of foods may be tested. An avoidance diet is only indicated in patients clearly identified as food allergic by an appropriate diagnostic food challenge, and after adequately informing the family of the limited benefits, and possible harms of an elimination diet.

Pancreatic Enzyme Supplementation in Patients with Atopic Dermatitis and Food Allergies: An Open-Label Pilot Study

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease that affects both patients and their families. Current therapies often alleviate symptoms but do not prevent or eradicate the disease.

OBJECTIVES

Our objective was to determine whether pancreatic enzyme supplementation is an effective and safe treatment in refractory pediatric AD associated with food allergies.

METHODS

We conducted an open-label pilot study using a case-control design. Patients with severe AD and known food allergies refractory to conventional therapies and exclusion diets were recruited and treated for 6 weeks with oral supplementation of pancreatic enzymes. The primary endpoint was the severity of AD, using the Scoring Atopic Dermatitis (SCORAD) index. Secondary measures included markers of intestinal permeability (urinary sucrose and lactulose/mannitol excretion).

RESULTS

A total of 11 patients met all eligibility criteria and completed the trial. Significant improvement in AD was observed after 6 weeks of pancreatic enzyme supplementation (SCORAD index 52.3 ± 5.5 vs. 34.6 ± 7.6; p = 0.0008). Beneficial effect was observed in 9 of 11 patients, without adverse events. Fractional urinary sucrose excretion improved to a level comparable to that of age-matched controls (p < 0.05). However, urinary lactulose:mannitol ratios remained abnormally high compared with those of controls (p = 0.01).

CONCLUSIONS

Pancreatic enzyme supplementation was associated with improved AD and gastroduodenal permeability. Additional randomized placebo-controlled studies are required before this treatment can be recommended in this clinical setting.

Soy, Soy Foods and Their Role in Vegetarian Diets

Soy is a basic food ingredient of traditional Asian cuisine used for thousands of years. In Western countries, soybeans have been introduced about a hundred years ago and recently they are mainly used for surrogate foods production. Soy and soy foods are common nutritional solutions for vegetarians, due to their high protein content and versatility in the production of meat analogues and milk substitutes. However, there are some doubts about the potential effects on health, such as the effectiveness on cardiovascular risk reduction or, conversely, on the possible disruption of thyroid function and sexual hormones. The soy components that have stimulated the most research interest are isoflavones, which are polyphenols with estrogenic properties highly contained in soybeans. In this review, we discuss the characteristics of soy and soy foods, focusing on their nutrient content, including phytoestrogens and other bioactive substances that are noteworthy for vegetarians, the largest soy consumers in the Western countries. The safety of use will also be discussed, given the growing trend in adoption of vegetarian styles and the new soy-based foods availability.

Clinical spectrum of food allergies: a comprehensive review

Food allergy is defined as an adverse immune response towards food proteins or as a form of a food intolerance associated with a hypersensitive immune response. It should also be reproducible by a double-blind placebo-controlled food challenge. Many reported that food reactions are not allergic but are intolerances. Food allergy often presents to clinicians as a symptom complex. This review focuses on the clinical spectrum and manifestations of various forms of food allergies. According to clinical presentations and allergy testing, there are three types of food allergy: IgE mediated, mixed (IgE/Non-IgE), and non-IgE mediated (cellular, delayed type hypersensitivity). Recent advances in food allergy in early childhood have highlighted increasing recognition of a spectrum of delayed-onset non-IgE-mediated manifestation of food allergy. Common presentations of food allergy in infancy including atopic eczema, infantile colic, and gastroesophageal reflux. These clinical observations are frequently associated with food hypersensitivity and respond to dietary elimination. Non-IgE-mediated food allergy includes a wide range of diseases, from atopic dermatitis to food protein-induced enterocolitis and from eosinophilic esophagitis to celiac disease. The most common food allergies in children include milk, egg, soy, wheat, peanut, treenut, fish, and shellfish. Milk and egg allergies are usually outgrown, but peanut and treenut allergy tends to persist. The prevalence of food allergy in infancy is increasing and may affect up to 15-20 % of infants. The alarming rate of increase calls for a public health approach in the prevention and treatment of food allergy in children.

Laboratorial characteristics of patients with diarrhoea suffering from egg white allergy

BACKGROUND

Egg allergy is associated with diarrhoeal symptoms. However, the mechanism underlying allergic diarrhoea remains unclear.

OBJECTIVE

To determine whether egg white-specific IgE antibodies coexist with egg white-specific IgG antibodies in patients with egg allergy featuring diarrhoeal symptoms, and whether there is any relationship between these two antibody types.

METHODS

A total of 89 patients with egg allergy featuring diarrhoeal symptoms (average age, 23.2 years; range, 1-78 years), all of whom tested positive for egg white-specific IgG, were enrolled in this study. The concentration of total IgE, egg white-specific IgE and number of eosinophils in the serum were determined.

RESULTS

Among the 89 egg white allergic patients tested, 49 (55.1%) patients showed high reactivity to egg white-specific IgG, 48 (53.9%) patients had elevated serum total IgE levels, and 25 (28.1%) patients had elevated absolute eosinophil numbers. Out of the 89 egg white allergic patients, 25 showed elevated egg white-specific IgE antibody levels. Of the 25 patients who were positive for egg white-specific IgE antibody, 21 presented high sensitive reaction to egg white-specific IgG, three presented moderate sensitive reaction to egg white-specific IgG, and one presented mild sensitive reaction to egg white-specific IgG. A moderate correlation between egg white-specific IgG and egg white-specific IgE, egg white-specific IgG and absolute eosinophil number was found in the egg white allergic patients (r=0.438, P=0.000; r=0.322, P=0.002). Egg white-specific IgE levels varied in different age groups; the egg white-specific IgE concentration of younger patients (age≤18 years, mean rank 54.29) was significantly higher than that of the adult patients (age>18 years, mean rank 34.61) (Z=-3.629, P=0.000).

CONCLUSION

Egg white-specific IgE antibody could coexist with egg white-specific IgG antibody in patients suffering from egg white allergy. Aberrant changes in the concentration of egg white-specific IgE antibody were associated with the presence of egg white-specific IgG antibody.

Allergic triggers in atopic dermatitis

Food or environmental allergens play a significant pathogenic role in a subgroup of patients with atopic dermatitis (AD) and can trigger eczema flares. This review focuses on when and which diagnostic and allergen-avoidance measures are beneficial. Diagnosis of allergic triggers may be aided by skin-prick tests measuring serum-specific IgE and/or atopy patch tests (APT) based on the patient's history, and when necessary, oral food challenges (OFC). In a subset of patients, therapeutic measures, such as elimination of the incriminated allergen(s), can lead to marked improvement of AD; this is especially true for food allergens, but can also apply to inhalant allergens.

Pediatric atopic dermatitis: the importance of food allergens

Food allergy and atopic dermatitis often occur in the same patients. Food-induced eczema may be perceived as a controversial topic because the immunologic mechanisms have yet to be fully elucidated. Nevertheless, published clinical studies have clearly demonstrated that foods can induce symptoms in a subset of patients with atopic dermatitis. Those at greatest risk are young children in whom eczematous lesions are severe or recalcitrant to therapy. Allergy testing can be helpful but must be applied judiciously. A medical history obtained by a skilled and knowledgeable health care provider is of paramount importance to interpret test results appropriately. Finally, the implementation of proper dietary avoidance can improve symptoms and provide safety from potentially fatal anaphylaxis. However, if inappropriate prescribed, elimination diets can have significant negative nutritional and social consequences.

Recent advances in the understanding of egg allergens: basic, industrial, and clinical perspectives

The emergence of egg allergy has had both industrial and clinical implications. In industrialized countries, egg allergy accounts for one of the most prevalent food hypersensitivities, especially in children. Atopic dermatitis represents the most common clinical manifestation in infancy; however, the range of clinical signs is broad and encompasses life-threatening anaphylaxis. The dominant egg allergens are proteins and are mainly present in the egg white, for example, ovalbumin, ovomucoid, ovotransferrin, and lysozyme. However, egg yolk also displays low-level allergenicity, for example, alpha-livetin. Strict avoidance of the offending food remains the most common recommendation for egg-allergic individuals. Nevertheless, the omnipresence of egg-derived components in prepackaged or prepared foods makes it difficult. Therefore, more efficient preventive approaches are investigated to protect consumers from inadvertent exposure and ensuing adverse reactions. On the one hand, commercial kits have become readily available that allow for the detection of egg contaminants at trace levels. On the other hand, attempts to produce hypoallergenic egg-containing products through food-processing techniques have met with promising results, but the approach is limited due to its potentially undesirable effects on the unique functional and sensory attributes of egg proteins. Therefore, the development of preventive or curative strategies for egg allergy remains strongly warranted. Pilot studies have suggested that oral immunotherapy (IT) with raw or cooked preparations of egg may represent a safe alternative, immediately available to allergic subjects, but remains applicable to only nonanaphylactic patients. Due to the limitations of conventional IT, novel forms of immunotherapy are sought based on information obtained from the molecular characterization of major egg allergens. In the past decade, promising approaches to the treatment and prevention of egg allergy have been explored and include, among others, the production of hypoallergenic recombinant egg proteins, the development of customized peptides, and bacterial-mediated immunotherapy. Nonspecific approaches have also been evaluated, and preliminary trials with the use of probiotic bacteria have yielded encouraging results. The current understanding of egg allergens offers novel approaches toward the making of food products safe for human consumption and the development of efficient immunotherapeutic strategies.

IgE food sensitization in infants with eczema attending a dermatology department

OBJECTIVES

Because community-based studies, which report IgE food sensitization (IgE-FS) in more than 80% of infants with moderate atopic eczema, may be influenced by referral bias, we assessed the prevalence of IgE-FS in a cohort of infants with moderate atopic eczema attending a dermatology department clinic.

STUDY DESIGN

Consecutive infants (n = 51, 39 males; median age, 34 weeks; range, 20 to 51 weeks) with moderate atopic eczema referred to a university-affiliated dermatology department were studied prospectively. Clinical history and eczema severity were documented. IgE-FS was assessed by the skin prick test (SPT; n = 51) and food-specific serum IgE antibodies (CAP-FEIA test; n = 41). IgE-FS was diagnosed if the SPT or CAP-FEIA level exceeded the >95% predictive reference cutoff for positive food challenges.

RESULTS

Based on SPT, 44 of 51 infants (86%; 95% confidence interval [CI] = 74% to 94%) had IgE-FS (cow's milk, 16%; egg, 73%; peanut, 51%). Using age-specific 95%-predictive cutoff values, CAP-FEIA identified 34 of 41 infants (83%; 95% CI = 68% to 93%) with IgE-FS (cow's milk, 23%; egg, 80%). Forty-six (90%) infants had IgE-FS to at least 1 food item by either SPT or CAP-FEIA.

CONCLUSIONS

Atopic eczema was found to be closely associated with IgE-FS in infants attending a dermatology department.

Sensitization in early age to food allergens in children with atopic dermatitis

BACKGROUND

Clinical and laboratory evidence increasingly supports the notion that food allergy plays a role in the pathogenesis of atopic dermatitis (AD). However, the prevalence of clinically significant food hypersensitivity among children with AD remains an unanswered question.

OBJECTIVE

To prospectively determine the prevalence of IgE-mediated food hypersensitivity among patients referred to a dermatology department for evaluation of AD, and to analyze the clinical relevance of these sensitizations in AD.

METHODS

We studied 44 infants of both sexes, aged less than 12 months old, who attended the dermatology department with symptoms of AD. Compliance with Hanifin-Rajka criteria was confirmed and the severity of AD was evaluated using the SCORAD index. IgE-mediated sensitization to cow's milk, alpha-lactalbumin, beta-lactoglobulin, casein, egg-white, egg-albumin, ovomucoid and foods introduced into the diet was studied using the skin prick test (SPT) and measurement of specific serum IgE (sIgE) by CAP System fluorescein-enzyme immunoassay. Cow's milk, as well as suspected foods from the clinical history or those with a positive SPT and/or sIgE, were withdrawn from the diet to evaluate improvement in AD, and an open controlled challenge test was carried out.

RESULTS

Of the 44 patients studied, sensitization to foods was detected in 27 (61 %). No changes were observed in AD during the elimination diet or when the eliminated foods were subsequently reintroduced into the diet. The results of open controlled food challenges were positive in 12 patients (27 %).

CONCLUSIONS

A high prevalence of food sensitization was found in infants with AD. The most frequent sensitization observed was to egg, although with little clinical relevance since this food had not been introduced into the diet. In the sample studied, the clinical relevance of the observed food hypersensitivities was confirmed in relation to AD. Further studies are required to confirm these results.

Atopic dermatitis

Atopic dermatitis is an especially common and frustrating condition, and the prevalence is increasing. The disease can adversely affect the quality of life of patients and caregivers. Significant advances in our understanding of the pathogenesis have led to improvements in therapy. Patient and caregiver education, avoidance of potential triggering factors, optimal skin care, and pharmacotherapy offer the potential for good control for most patients.

Atopic dermatitis: review of immunopathogenesis and advances in immunosuppressive therapy

This paper reviews the theories of the pathogenesis of atopic dermatitis (AD), with a particular emphasis on its immunopathogenesis. The contribution of predisposing factors, immunopathogenic factors and provoking factors in the pathogenesis of AD are considered. Predisposing factors explored in this article include genetics and the disturbance of skin function. Immunopathogenic factors reviewed include T cell dysfunction, biphasic cytokine expression and the role of immunoglobulin E. Provoking factors considered include microbial factors, psychosomatic interactions, contact allergens and irritants, inhalant allergens, food and climate. Immunosuppressive treatments reviewed include cyclosporin, azathioprine, methotrexate, tacrolimus, interferon-gamma, phosphodiesterase inhibitors and pimecrolimus (SDZ ASM 981).

Effect of exclusive breast-feeding and early solid food avoidance on the incidence of atopic dermatitis in high-risk infants at 1 year of age

The aim of this study was to assess the preventive effect of exclusive breast-feeding and early solid food avoidance on atopic dermatitis (AD) in infancy. This study is part of a dietary clinical trial in a prospective cohort of healthy term newborns at risk of atopy. It was recommended to breast-feed for at least 4 months and to avoid solid food in the same time-period. Eight hundred and sixty-five infants exclusively breast-fed, and 256 infants partially or exclusively formula-fed, were followed-up until the end of the first year following birth. AD and sensitization to milk and egg were considered as study end-points. The 1-year incidence of AD was compared between the two study groups. Adjusted odds ratios (OR) with 95% confidence intervals (CI) were calculated by multiple logistic regression. The incidence of AD was calculated in relation to age at introduction of solid food and amount of food given. In the breast-fed group, the adjusted OR for AD was 0.47 (95% CI 0.30-0.74). The strongest risk factor was the occurrence of AD in the subject's core family. The risk of infants with AD to be sensitized to milk was four times higher, and to egg eight times higher, than in infants without AD. Age at first introduction of solid food and diversity of solid food showed no effect on AD incidence. We conclude that in infants at atopic risk, exclusive breast-feeding for at least 4 months is effective in preventing AD in the first year of life.

[Etiologic implication of foods in atopic dermatitis: evidence against]

Atopic dermatitis is a typical chronic inflammatory skin disease that usually occurs in individuals with a personal or family history of atopy. Children with atopic dermatitis frequently present IgE-mediated food sensitization, the most commonly involved foods being egg and cow's milk. However, controversy currently surrounds whether food allergy is an etiological factor in atopic dermatitis or whether it is simply an associated factor, accompanying this disease as one more expression of the patient's atopic predisposition. Approximately 40 % of neonates and small children with moderate-to-severe atopic dermatitis present food allergy confirmed by double-blind provocation tests but this allergy does not seem to be the cause of dermatitis since in many cases onset occurs before the food responsible for allergic sensitization is introduced into the newborn's diet.Studies of double-blind provocation tests with food in patients with atopic dermatitis demonstrate mainly immediate reactions compatible with an IgE-mediated allergy. These reactions occur between 5 minutes and 2 hours and present mainly cutaneous symptoms (pruritus, erythema, morbilliform exanthema, wheals) and to a lesser extent, digestive manifestations (nausea, vomiting, abdominal pain, diarrhea), as well as respiratory symptoms (wheezing, nasal congestion, sneezing, coughing). However, these reactions do not indicate the development of dermatitis.Some authors believe that responses to the food in provocation tests may also be delayed, appearing mainly in the following 48 hours, and clinically manifested as exacerbation of dermatitis. However, delayed symptoms are difficult to diagnose and attributing these symptoms to a particular foodstuff may not be possible.Delayed reactions have been attributed to a non-IgE-mediated immunological mechanism and patch tests with food have been proposed for their diagnosis. In our experience and in that of other authors, the results of patch tests with cow's milk do not seem very specific and could be due, at least in part, to the irritant effect of these patches on the reactive skin of children with atopic dermatitis.The involvement of foods in atopic dermatitis will always be difficult to demonstrate given that an exclusion diet is not usually required for its resolution. Food is just one among several possible exacerbating factors and consequently identification of its precise role in the course of the disease is difficult. Further double-blind prospective studies are required to demonstrate the effectiveness of exclusion diets in the treatment of atopic dermatitis.Apart from the controversy surrounding the etiological role of foods, the most important point in atopic dermatitis is to understand that the child is atopic, that is, predisposed to developing sensitivity to environmental allergens; in the first few years of life to foods and subsequently to aeroallergens. Consequently, possible allergic sensitization to foods should be evaluated in children with atopic dermatitis to avoid allergic reactions and to prevent the possible development of allergic respiratory disease later in life.

Milk-induced urticaria is associated with the expansion of T cells expressing cutaneous lymphocyte antigen

BACKGROUND

Two forms of IgE-mediated skin reactions, atopic dermatitis (AD) and urticaria, have been associated with milk allergy. The reason for these distinct reactions is poorly understood. T cells expressing cutaneous lymphocyte antigen (CLA), a unique skin-homing receptor, are known to play an important role in AD. In contrast, the role of lymphocytes in patients with milk-induced urticaria is unclear.

OBJECTIVE

The expression of the skin-specific homing receptor CLA after in vitro milk protein-specific stimulation was investigated to determine whether T-lymphocyte homing to the skin plays a role in food-induced urticaria.

METHODS

Fourteen patients with milk-induced urticaria but no evidence of AD were included in the study and compared with 6 children with milk-induced AD, 6 children with milk-induced gastrointestinal diseases, and 6 nonatopic and 6 atopic individuals without milk allergy. PBMCs were cultured in the presence or absence of caseins or tetanus toxoid. T-cell proliferation was determined, and T-cell phenotyping was performed by means of flow cytometry with anti-CD4, anti-CD8, and anti-CLA mAbs.

RESULTS

After in vitro stimulation with caseins, PBMCs from patients with milk-induced urticaria and AD had a significantly greater percentage of CD4(+) T cells expressing CLA than patients with milk-induced gastrointestinal symptoms and atopic or nonatopic control subjects. After tetanus stimulation in vitro, no significant difference between the groups was observed. T cells from both patients with milk-induced urticaria and control subjects proliferated well in response to caseins and tetanus.

CONCLUSION

Lymphocytes expressing CLA are selectively activated in patients with milk-induced urticaria and may play an important role in the pathogenesis of this disease. Expression of CLA is not unique to milk-induced inflammation in the skin of patients with AD and milk allergy.

The association of atopic dermatitis in infancy with immunoglobulin E food sensitization

OBJECTIVE

To prospectively investigate the association of high levels of immunoglobulin E (IgE) sensitization to foods and the presence of atopic dermatitis (judged by reported topical steroid use during the first 16 months of life) in a birth cohort of 620 Australian children "at risk" of allergic disease because of family history.

RESULTS

A total of 559 of the children in the cohort were fully evaluated, and the cumulative prevalence of atopic dermatitis was 24%. More children in the cohort who had atopic dermatitis had strongly positive skin test results (> or = 4+, histamine equivalent units, > or = approximately 6-mm wheal), consistent with IgE food sensitization to either cow's milk, egg, or peanut at 6 months (22% vs 5%, chi(2) = 35; P < 10(-6)) and at 12 months (36% vs 11%, chi(2) = 41; P < 10(-6)) than those without atopic dermatitis. The calculated attributable risk percent for IgE food sensitization as a cause of atopic dermatitis was 65% and 64% at these times. In a separate group of infants with severe atopic dermatitis, the equivalent rates of IgE food sensitization at 6 months was 83% and at 12 months, 65%.

CONCLUSION

IgE food sensitization is a major risk factor for the presence of atopic dermatitis in infancy.

Managing pediatric atopic dermatitis

Although atopic dermatitis is a very common inflammatory skin condition in children and results in many pediatric healthcare visits, its exact cause is unknown. No single laboratory test can reliably diagnose atopic dermatitis, but a relatively simple set of diagnostic criteria was recently validated for use by practicing physicians. Because existing remedies for atopic dermatitis do not cure the disorder, a program of disease control and management should be pursued. Patients and their caregivers should be advised that current therapies are primarily preventive and palliative. However, a comprehensive plan that includes routine general skin care, medical management of symptoms, identification and avoidance of aggravating factors (including psychological factors), and attention to quality-of-life issues can reduce the occurrence of skin flares. Successful treatment of acute flare-ups can be achieved with appropriate use of topical corticosteroids, but occasionally children afflicted with severe atopic dermatitis require more intensive therapies (e.g., ultraviolet light exposure systemic corticosteroids, and cyclosporine) that need close physician monitoring. Physicians must remain mindful of the psychological and quality-of-life burdens imposed on children with atopic dermatitis and their families and tailor treatments to the needs of each individual patient.

Clinical aspects, epidemiology, and prognosis of atopic dermatitis

OBJECTIVE

This review article examines the clinical aspects, epidemiology, and prognosis of atopic dermatitis.

DATA SOURCES

These are studies and review articles from textbooks of dermatitis and allergy in general, as well as more recent epidemiologic surveys published in specialist journals of allergy and dermatology.

STUDY SELECTION

Included studies meet the criteria of being a survey of the prevalence of atopic dermatitis published recently in a respected peer-reviewed journal. Particular emphasis is placed on those that examine both the prevalence of the problem and significant causative and associated factors.

RESULTS

Atopic dermatitis is frequently a severe illness that develops in early infancy. It can persist beyond the childhood years and is often found in association with significant respiratory complications. The exact pathogenesis is unclear but it appears that it has a complex immunologic origin. Early surveys lack the methodologic refinements of more recent data from the mid-1990s, including the SCARPOL study. Collectively, these point to a high current prevalence rate of 10% to 15%, a figure that has risen steadily in the preceding decades. The most common associations of atopic dermatitis are a risk of developing respiratory disorders, such as allergic rhinitis and asthma (40% to 60%), and a persistence rate after puberty (40% to 60%), which is indeed much higher than previously suspected.

CONCLUSIONS

A clear recognition of the various disease subgroups along with intervention studies that evaluate reduction of risk are needed before more precise treatment strategies can be devised.

Clinical spectrum of food allergy in children in Australia and South-East Asia: identification and targets for treatment

The prevalence of atopic diseases is increasing worldwide for reasons that are not clear. Food allergies are the earliest manifestations of atopy. This review defines the foods most commonly involved in allergic reactions and identifies an emerging group of syndromes in which food allergy is involved. A study of the frequency of food allergies in Australia and South-East Asia has recently shown that egg, cow's milk and peanut are the most common food allergens in Australia, but there were divergent results from different regions of South-East Asia. It is not clear whether the differences in reactivity to foods are due to genetic or cultural factors, but the findings raise the possibility that genetic susceptibility to food allergy may operate at the T-cell level modulated by the major histocompatibility complex. The Melbourne Milk Allergy Study defined a wide range of clinical symptoms and syndromes that could be reproduced by dietary challenge. A subsequent analysis of the infants with hypersensitivity to cow's milk and other multiple food proteins identified a new syndrome, multiple food protein intolerance of infancy. Food challenges demonstrated reactions developing slowly days after commencement of low-allergen soy formula or extensively hydrolysed formula. Follow-up at the age of 3 years showed that most children with this disorder tolerated most foods apart from cow's milk, egg and peanut. Atopic dermatitis affects about 18% of infants in the first 2 years of life. In a community-based study we have shown a very strong association (RR 3.5) between atopic dermatitis and infants with immunoglobulin E allergy to cow's milk, egg or peanut. Family studies on these infants have shown a link between atopic dermatitis and the genomic region 5q31 adjacent to the interleukin-4 gene cluster. Infantile colic (distress) affects 15-40% of infants in the first 4 months of life. Many theories of causation have been proposed, but a study from our centre showed that dietary modification, particularly that of breastfeeding mothers whose infants present with colic before the age of 6 weeks, alleviated symptoms. Colic associated with vomiting has been attributed to gastro-oesophageal reflux (GOR). This has been considered primarily a motility disorder, but a secondary form resulting from food protein intolerance has been described recently. We have also recently identified a group of infants with distressed behaviour attributed to GOR who have failed to respond to H2-receptor antagonists, prokinetic agents and multiple formula changes. Symptoms resolved on commencement of an elemental amino acid-based formula. In two-thirds of the patients, symptoms relapsed when challenged with low-allergen soy formula or extensively hydrolysed formula. We propose that a period of food protein intolerance is a part of the normal development of the immune system as it encounters common dietary proteins in infancy and early childhood. Future targets for research are development of appropriate dietary and management strategies for these entities and identification of genetic markers for these disorders.

Food-induced cutaneous adverse reactions

The skin is the most frequently affected target organ in allergy or intolerance of food and food additives. The most common manifestation is acute urticaria (with or without angioedema), accounting for 40-60% of patients with IgE-mediated food allergy, whereas food additives rather aggravate chronic urticaria (intolerance provocation). The role of food allergy in the pathogenesis of atopic dermatitis is still controversial; however, there is no doubt that, particularly in infants and young children, food allergens can induce atopic dermatitis or aggravate skin lesions. In adults, food allergy as a cause or a trigger of atopic dermatitis is very rare. However, in food-allergic patients with atopic dermatitis, the ingestion of the food item can provoke the whole spectrum of IgE-mediated symptoms, from oral allergy syndrome to severe anaphylaxis. Skin symptoms can also be induced not only after food ingestion in sensitized people, but also after direct skin contact, as lipophilic food allergens can penetrate the skin via the hair follicles or when the skin barrier function is defective. Immediate contact reactions of the skin are a heterogeneous group: they include not only contact urticaria (contact urticaria syndrome) on an immunologic or nonimmunologic basis, but also allergic or nonallergic eczematous reactions caused by food proteins (protein contact dermatitis). A prototype is baker's eczema in a restricted sense with immediate-type sensitization to flour. Atopic eczema provoked by direct contact of the skin with food must also be taken into consideration. Finally, very rarely, allergic contact dermatitis that is due to type IV sensitization to food or food additives (positive delayed type reaction in the patch tests) can occur. The oral ingestion of these foods may provoke in these patients a generalized eczematous rash or dyshidrosiform reactions (vesicles) of the fingers, palms, and soles.