What is the most likely outcome of administering an antihistamine 1 day before an allergy test?

Administering an antihistamine one day before an allergy test is likely to interfere with the test results, leading to unreliable outcomes. Antihistamines work by blocking histamine receptors in the body, which are crucial for eliciting allergic reactions. When a person is tested for allergies, the response is ideally assessed by observing how the immune system reacts to specific allergens.

By taking antihistamines prior to the test, the normal allergic response may be suppressed, resulting in a diminished or altered reaction to allergens. This suppression can mask true sensitivities, hence affecting the accuracy of the test results. Consequently, the healthcare provider may either not be able to identify existing allergies or misinterpret the results, thinking the individual does not have an allergy when they actually do.

The interference caused by antihistamines underscores the importance of following pre-test guidelines, which often recommend avoiding these medications for a certain period prior to allergy testing to ensure the results are reflective of the patient’s true allergic response.