Rate of patch test reactions to a Dermatophagoides mix currently on the market: A mite too sensitive?

Background: There long has been debate over the role of the dust mite antigen Dermatophagoides in provoking or perpetuating atopic and other forms of dermatitis, particularly airborne contact dermatitis. Reactivity to Dermatophagoides has been measured by specific IgE and by immediate-type responses to prick test challenge. More recently, patch testing has been advocated as a means of determining reactivity to Dermatophagoides.Objective: To determine patch test reactivity to a Dermatophagoides mix in a population receiving patch testing. Methods: A commercially available mix of 2 species of Dermatophagoides, Dermatophagoides pteronyssinus and Dermatophagoides farinae, recently became available. The authors chose the lower available concentration of this mix (20%) and added it to their standard patch testing tray between December 1999 and January 2001. Results were interpreted in the standard manner. Results: A total of 662 patients received patch testing to Dermatophagoides (men 32%, women, 68%). Mean age was 53.4 years (range, 37 to 94). The Dermatophagoides mix was the most common allergen in the standard tray to evoke a reaction. At 96 hours, positive reactions were noted in 55% of patients. The reactions were interpreted as irritant in 16.2%, relevant in 6.7%, of questionable relevancy in 30.5%, and of no relevancy in 32.6%. The majority of reactions were of the [ldquo ]crescendo[rdquo ] pattern. Conclusion: The currently available formulation of Dermatophagoides mix, even at its lower concentration, led to a high rate of reactivity with a low rate of relevance.