Patch test reactions to inhalant allergens in atopic dermatitis

Area of Science:

• Immunodermatology
• Allergology
• Clinical immunology

Background:

• Atopic dermatitis (AD) is a chronic inflammatory skin condition.
• The role of inhalant allergens in exacerbating AD in patients not experiencing active flares is not fully understood.
• Epicutaneous testing with high-concentration allergens may reveal subclinical sensitization.

Purpose of the Study:

• To investigate if inhalant allergens (birch pollen, house dust mite) can induce eczematous reactions on normal skin in atopic patients.
• To determine the prevalence of positive patch test reactions to these allergens in patients with AD and allergic rhinitis.
• To analyze skin biopsy findings in patients with positive reactions.

Main Methods:

• Epicutaneous patch testing with birch pollen and house dust mite antigens at 500x prick test concentration.
• Inclusion of patients with atopic dermatitis in remission, atopic patients with allergic rhinitis, and healthy controls.
• Skin biopsy and immunofluorescence staining of lesional skin.

Main Results:

• Positive delayed-type reactions observed in 6/17 (35%) atopic dermatitis patients to birch pollen and 3/17 (18%) to house dust mite.
• Only 1/13 (8%) atopic patients with allergic rhinitis showed a positive reaction to birch pollen; none to house dust mite.
• No positive reactions in healthy controls. Biopsies showed epidermal spongiosis, vesiculation, and CD1/HLA-DR positive keratinocytes.

Conclusions:

• Inhalant allergens can induce eczematous reactions in the skin of atopic dermatitis patients, even during remission.
• These findings suggest that inhalant allergens may play a significant role in exacerbating atopic dermatitis.
• The presence of CD1 and HLA-DR on keratinocytes indicates an inflammatory response potentially involving antigen presentation.