ECZEMA AND FOOD HYPERSENSITIVITY

Position document: IgE-mediated cow's milk allergy

The present document offers an update on the recommendations for managing patients with cow's milk allergy - a disorder that manifests in the first year of life, with an estimated prevalence of 1.6-3% in this paediatric age group. The main causal allergens are the caseins and proteins in lactoserum (beta-lactoglobulin, alpha-lactoalbumin), and the clinical manifestations are highly variable in terms of their presentation and severity. Most allergic reactions affect the skin, followed by the gastrointestinal and respiratory systems, and severe anaphylaxis may occur. The diagnosis of cow's milk allergy is based on the existence of a suggestive clinical history, a positive allergy study and the subsequent application of controlled exposure testing, which constitutes the gold standard for confirming the diagnosis. The most efficient treatment for cow's milk allergy is an elimination diet and the use of adequate substitution formulas. The elimination diet must include milk from other mammals (e.g., sheep, goat, etc.) due to the risk of cross-reactivity with the proteins of cow's milk. Most infants with IgE-mediated cow's milk allergy become tolerant in the first few years of life. In those cases where cow's milk allergy persists, novel treatment options may include oral immunotherapy, although most authors do not currently recommend this technique in routine clinical practice. Enough evidence is not there to confirm the efficacy of elimination diets in the mother and infant for preventing the appearance of cow's milk allergy. Likewise, no benefits have been observed with prebiotic and probiotic dietetic supplements in infants for preventing food allergy.

Food allergy--accurately identifying clinical reactivity

Up to 25% of adults believe that they or their children are afflicted with a food allergy. However, the actual prevalence of food allergy is much lower: approximately 6-8% of children suffer from food allergy during their first 3 years of life, and many children then develop clinical tolerance. Food allergy encompasses a whole spectrum of disorders, with symptoms that may be cutaneous, gastrointestinal or respiratory in nature. Food disorders also differ according to the extent that they are immunoglobulin E (IgE)-mediated. Skin-prick testing is often used to identify food sensitization, although double-blind, placebo-controlled food challenge (DBPCFC) tests remain the gold standard for diagnosis. Recent evidence suggests that quantitative IgE measurements can predict the outcome of DBPCFC tests and can replace about half of all oral food challenges. When an extensive medical history is obtained in combination with IgE quantification, even fewer patients may require formal food challenges. It has also become possible to map the IgE-binding regions of many major food allergens. This may help to identify children with persistent food allergy, as opposed to those who may develop clinical tolerance. In future, microarray technology may enable physicians to screen patients for a large number of food proteins and epitopes, using just a few drops of blood.

Food allergies and food intolerances

Adverse reactions to foods, aside from those considered toxic, are caused by a particular individual intolerance towards commonly tolerated foods. Intolerance derived from an immunological mechanism is referred to as Food Allergy, the non-immunological form is called Food Intolerance. IgE-mediated food allergy is the most common and dangerous type of adverse food reaction. It is initiated by an impairment of normal Oral Tolerance to food in predisposed individuals (atopic). Food allergy produces respiratory, gastrointestinal, cutaneous and cardiovascular symptoms but often generalized, life-threatening symptoms manifest at a rapid rate-anaphylactic shock. Diagnosis is made using medical history and cutaneous and serological tests but to obtain final confirmation a Double Blind Controlled Food Challenge must be performed. Food intolerances are principally caused by enzymatic defects in the digestive system, as is the case with lactose intolerance, but may also result from pharmacological effects of vasoactive amines present in foods (e.g. Histamine). Prevention and treatment are based on the avoidance of the culprit food.

Induction of cutaneous delayed hypersensitivity reactions in mice sensitized with intragastrically administered hapten: activation of Langerhans cells in the sensitization and elicitation phases

BACKGROUND

As seen in atopic dermatitis, allergic diseases often produce lesions both in the gastrointestinal tract and the skin, suggesting the involvement of an immunological relationship between the two organs in the pathogenesis.

OBJECTIVES

To study the role of gastric and epidermal Langerhans cells (LCs) in the sensitization and elicitation phases, respectively, of cutaneous delayed-type hypersensitivity (DTH) reactions to intragastrically administered hapten.

METHODS

BALB/c mice, which were subjected to intragastric administration of trinitrochlorobenzene 5 days previously, received an elicitative challenge of the same hapten to the ear skin. Sections of the ear were immunostained for CD4 and CD8. Epidermal sheets of the ear and epithelial sheets of the forestomach were immunostained for I-A and observed under a confocal laser scanning microscope.

RESULTS

Cutaneous DTH reactions were induced in mice, as demonstrated by an increase in ear thickness and a prominent infiltration of CD4+ and CD8+ lymphocytes at 24-36 h after the elicitative challenge. In the elicitation phase, epidermal LCs showed a significant increase in size, indicating in vivo activation, at 24 h. In the sensitization phase, gastric LCs increased in size at 2 h, became round at 6 h, and decreased in number at 24 h, possibly representing the sequential events of LC activation and migration from the epithelium.

CONCLUSIONS

The present study demonstrated that gastric LCs and epidermal LCs were activated in vivo in the sensitization and elicitation phases, respectively, of cutaneous DTH reactions in orally sensitized mice.

9. Food allergy

Food allergies affect as many as 6% of young children, most of whom "outgrow" the sensitivity, and about 2% of the general population. Although any food may provoke a reaction, relatively few foods are responsible for the vast majority of food allergic reactions: milk, egg, peanuts, tree nuts, fish, and shellfish. Many of these food allergens have been characterized at a molecular level, which has increased our understanding of the immunopathogenesis of many responses and may soon lead to novel immunotherapeutic approaches. Food allergic reactions are responsible for a variety of symptoms involving the skin, gastrointestinal tract, and respiratory tract and may be due to IgE-mediated and non-IgE-mediated mechanisms. A systematic approach including history, laboratory studies, elimination diets, and often food challenges will lead to the correct diagnosis. Currently, management of food allergies consists of educating the patient to avoid ingesting the responsible allergen and to initiate therapy in case of an unintended ingestion.

Murine model of atopic dermatitis associated with food hypersensitivity

BACKGROUND

Atopic dermatitis (AD) is an eczematous skin eruption that generally begins in early infancy and affects up to 12% of the population. The cause of this disorder is not fully understood, although it is frequently the first sign of atopic disease and is characterized by an elevated serum IgE level, eosinophilia, and histologic tissue changes characterized early by spongiosis and a CD4(+) T(H)2 cellular infiltrate. Hypersensitivity to foods has been implicated as one causative factor in up to 40% of children with moderate-to-severe AD.

OBJECTIVE

The purpose of this study was to establish a murine model of food-induced AD.

METHODS

Female C3H/HeJ mice were sensitized orally to cow's milk or peanut with a cholera toxin adjuvant and then subjected to low-grade allergen exposure. Histologic examination of skin lesions, allergen-specific serum Ig levels, and allergen-induced T-cell proliferation and cytokine production were examined.

RESULTS

An eczematous eruption developed in approximately one third of mice after low-grade exposure to milk or peanut proteins. Peripheral blood eosinophilia and elevated serum IgE levels were noted. Histologic examination of the lesional skin revealed spongiosis and a cellular infiltrate consisting of CD4(+) lymphocytes, eosinophils, and mast cells. IL-5 and IL-13 mRNA expression was elevated only in the skin of mice with the eczematous eruption. Treatment of the eruption with topical corticosteroids led to decreased pruritus and resolution of the cutaneous eruption.

CONCLUSION

This eczematous eruption resembles AD in human subjects and should provide a useful model for studying immunopathogenic mechanisms of food hypersensitivity in AD.

Effect of allergist intervention on patient-centered and societal outcomes: allergists as leaders, innovators, and educators

Atopic disorders, which afflict millions of Americans and hundreds of millions worldwide, are at epidemic levels with concomitant increases in morbidity and mortality. Environmental and lifestyle changes over the past three to five decades are proposed causes for this pandemic and as such present major burdens to reverse. The scope of allergy practice bridges directly on this challenge. Allergy as a specialty is a major leader in developing effective strategies to confront this epidemic. Allergists have made major contributions to the understanding of the risk factors, immunology, pathophysiology, immunomodulation, and prevention of atopic and immunologic disorders. Allergist epidemiologists and clinicians have helped develop and implement national and international guidelines in the recognition, management, and prevention of asthma and rhinitis. Allergist clinical researchers are active in (1) outcomes research that demonstrates convincingly the value of allergy as a specialty in asthma, allergic rhinitis, anaphylaxis, drug and food allergy, and other atopic disorders, (2) National Institutes of Health clinical trials that will form the basis for the future treatment of asthma and allergic disease, and (3) pharmaceutical trials that evaluate new, effective, and safe medication to treat atopic disease. Allergist educators, comprising academic and practicing allergists, supported by allied health professionals, national associations, and affiliated lay organizations, provide comprehensive education to fellows, residents, colleague physicians, media, the public, and patients. Documentation of the value of allergists in improving patient-centered and societal outcomes in their core domain, allergy, is the appropriate final topic contribution in the important series "New millennium: The conquest of allergy."