allergic purpura [Gk, allos, other, ergein, to work; L, purpura, purple] , a chronic disorder of the skin associated with urticaria, erythema, asthma, and rheumatic joint swellings. Unlike in other forms of purpura, the platelet count, the bleeding time, and blood clotting are normal. Sensitization to foods, drugs, and insect bites is a factor.
