The patient should not hesitate, however, to use the medication immediately, as directed by the physician. Immunotherapy involves injecting the allergen, such as insect venom, in increasing amounts over a period of years. The injected allergen stimulates production of IgG antibodies, which confer protection from the substance. Unlike allergen immunotherapy, desensitization is done in the hospital over a short period, beginning with extremely diluted solutions of the allergen. The patient is watched carefully as the dose is gradually increased and may be treated with antihistamines or other medicines if symptoms occur.
Experts disagree about whether certain individuals are predisposed to anaphylaxis.
This may indicate that future exposure will produce a more severe reaction. Marian Segal is a member of FDA's public affairs staff.