Current data concerning cutaneous
allergy to
insulin may be illustrated by the two cases reported here. One was a woman with
gestational diabetes; she was treated with bovine
insulin and developed generalized
urticaria which subsided after switching to human
insulin. The other was a woman who had
pruritus localized to the site of injection with every type of
insulin and in whom laboratory examinations showed an increase of specific
IgE. Immunological reactions have been described since the time when exogenous
insulin was introduced as a treatment of diabetes. The wide use of purified human
insulin has considerably reduced their incidence but benign local and immediate systemic reactions are still being reported, their estimated frequency varying from 10 p. 100 to 50 p. 100 of the patients treated. In reality,
allergy to
insulin itself is extremely rare compared with
allergic reactions to preservatives, such as
metacresol, additives (
protamine and
zinc and contaminants present in
insulin preparations:
desamido-insulin. True
allergic reactions to
insulin may be localized or generalized and biphasic, and in most cases they are
IgE-mediated. Some late local reactions, as well as
atrophy, can be ascribed to
delayed hypersensitivity. Treatment includes: (i) change in the type of
insulin used; (ii) systemic or topical
corticosteroid therapy; (iii)
antihistamines and
aspirin, and (iv) desensitization. The allergic complications of
insulin therapy are benign; they usually do not require any particular treatment and often spontaneously regress.