Patch testing with dermatophagoides and its correlation with chronic eczema and atopic dermatitis

Background: Chronic eczema is commonly encountered in the Indian set up. So also is atopic dermatitis. House dust mites (Dermatophagoides) are implicated in various diseases like atopic dermatitis, asthma, and perennial rhinitis. It has also been proven that patch testing with Dermatophagoides pteronyssinus (DP) is important for detection of contact sensitization in chronic dermatitis. Aims: To study clinical characteristics of DP mix positive patients with regards to chronic dermatitis and atopic dermatitis. Methods: Dermatology outpatients presenting to the department of Skin and STD of Kasturba Medical College (KMC), with clinically diagnosed atopic dermatitis and chronic eczema were chosen for the study. Inclusion and exclusion criteria were well demarked. Eighty six randomly selected patients of dermatitis were subjected to patch testing with standard series and DP mix. Results: Of the 86, 50 (58%) showed positive reaction to DP mix. Among these positive patients, chronic dermatitis was seen in 42 (84%) with involvement of exposed parts in 37 (74%). Atopic dermatitis was seen in 19 patients (38%) from DP positive group whereas it was observed in 4 patients (17%) from the other group. Conclusion: Dermatophagoides mix positivity was statistically significant in chronic eczema as well as atopic dermatitis. Patch testing is an important tool to detect delayed type allergy to house dust mite.