intradermal test [L, intra + Gk, derma, skin] , a procedure used to identify suspected allergens by subcutaneously injecting the patient with small amounts of extracts of the suspected allergens. The injections are made at spaced intervals, usually in the forearm or the scapular region. The patient is concurrently injected with the diluent alone as a control procedure. The test result is positive if within 15 to 30 minutes the injection of extract produces a wheal surrounded by erythema and the control injection produces no symptoms. The intradermal test is started with highly diluted solutions; if the initial test result is negative, the procedure is repeated with stronger solutions. This gradual method is used to prevent a systemic reaction, which is more of a risk with intradermal testing than with other kinds of allergy testing, such as the scratch test. The intradermal test tends to be more accurate than the scratch test and is often performed if scratch test results are negative or unclear. Intradermal testing also limits to between 20 and 30 the number of suspected allergens that can be examined simultaneously in the skin of one patient. Also called subcutaneous test. Compare patch test, scratch test. See also conjunctival test, use test.
