ALLERGY TO FEATHERS

Skin prick test reactivity to commercial and self-made feather-allerge n extracts was examined in 269 consecutive adult patients with suspect ed allergic cutaneous or respiratory symptoms who had been referred to a university clinic. Some 177 subjects reacted to any inhalant allerg en. Twenty-four (9% of the whole group and 14% of those positive to an y inhalant allergen) reacted to commercial feather extracts from ALK ( Horsholm, Denmark), and 51 to any of the seven feather extracts used. Feather-mix RAST (Pharmacia, Sweden) was positive in three cases only. Skin prick test or CAP-RAST or both to house-dust mite were positive in 16 of those 24 subjects positive to the commercial feather extracts , but in only 23 of the 150 other atopic subjects (P<0.001). A nasal c hallenge with a feather extract was made in 20 cases, always with nega tive result. In immunospot studies, concomitant allergy to feather-all ergen extracts and house-dust mite could be demonstrated. Mite allerge ns in feather extracts were verified in RAST-inhibition studies. A cli nically significant feather allergy was found in one patient only. The results suggest that true feather allergy is very rare, and most of t he positive reactions seen in skin prick tests to feather extracts are probably caused by mite allergens present in feathers.