Role of allergy in atopic dermatitis (eczema)

Multiple images of urticaria are shown. Urticarial lesions may be rounded (F) or irregular (A) in shape, and uniform or mixed (G) in morphology. Individual lesions may be small (H) or large (D). Urticaria are raised plaques, although they may appear flattened in patients taking antihistamines (C). Although lesions are consistently erythematous, this may be difficult to appreciate on darkly pigmented skin (I). Some urticaria show central clearing (E).
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SUMMARY

● Although there has been some controversy with regard to the role of allergy in atopic dermatitis (AD; eczema), the bulk of the data indicate that allergy plays a role in selected patients with AD.

● Infants and young children with AD are more commonly sensitized to foods, whereas children over five years and adults are more commonly sensitized to aeroallergens. However, evidence of allergen sensitization is not proof of clinically relevant allergy.

● In patients with AD, the rate of sensitization to foods (positive skin or in vitro test) ranges from 30 to 80 percent, depending upon the population. The rate of confirmed food allergy is much lower. Food allergies play a role in exacerbating AD in up to 33 percent of patients with severe AD, 10 to 20 percent with moderate AD, and 6 percent with mild AD. Elimination of food allergens in patients with AD and confirmed food allergy can lead to significant clinical improvement.

● Foods should not be eliminated from the diet randomly without any clinical suspicion. Nor should foods be excluded from the diet long term (as opposed to short term for diagnostic purposes) based upon positive skin or in vitro tests or patient history alone. Test results should be correlated with the clinical history and clinical reactivity confirmed when necessary by double-blind, placebo-controlled food challenge (DBPCFC) or elimination/challenge test.

● The data on the role of aeroallergens in exacerbating AD are less extensive. Dust mites are consistently the most common positive aeroallergen and also appear to be the most clinically relevant. Immune reactions, both immunoglobulin E (IgE) and T cell mediated, to Malassezia species can also worsen AD.

Urticaria – Multiple images – Multiple images of urticaria are shown. Urticarial lesions may be rounded (F) or irregular (A) in shape, and uniform or mixed (G) in morphology. Individual lesions may be small (H) or large (D). Urticaria are raised plaques, although they may appear flattened in patients taking antihistamines (C). Although lesions are consistently erythematous, this may be difficult to appreciate on darkly pigmented skin (I). Some urticaria show central clearing (E).

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