How many minimum days should an antihistamine be discontinued prior to an allergy test?

The minimum duration for discontinuing an antihistamine prior to an allergy test is typically four days. This is essential because antihistamines can interfere with the test results by blocking the action of histamine, which is a key component in allergic reactions. When an allergy test is performed, particularly skin prick tests, the presence of antihistamines in the system can lead to false negatives, as the body may not respond normally to the allergens being tested.

Discontinuing antihistamines for at least four days allows the body to metabolize and eliminate the medication, enabling a more accurate assessment of the individual's sensitivity to allergens. This timeframe is generally accepted in clinical practice to ensure that the results reflect the true allergic status of the patient.