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Gearing yourself up to take an allergy test means that you have to approach two things: the test and its results. If you are feeling nervous about the allergy test itself, it can be helpful to educate yourself on the test with its process and what to expect. However, even the average person has to understand the relationship between the allergy test and antihistamines.

The basics:

The use of antihistamines can impact a skin prick allergy test. A skin prick in and of itself is often thought of as being so-so in terms of giving accurate results, particularly with food allergies or mild allergies (food ones or otherwise). A skin prick test can also offer false positives due to reactions to the needle and not the injected allergen at the site.

If someone has especially sensitive skin or is prone to skin-based reactions, it can also produce inaccurate results and discomfort during the test itself.

The role of antihistamines

As you probably already know, antihistamines are given or taken in order to help minimize allergic reactions such as rashes, discomfort or congestion as antihistamines are designed to get rid of histamines (and stop the reaction, as a result), taking them before an allergy test will prevent a reaction altogether.

Due to this, a lot of allergists and professional allergy test providers will recommend that those who are interested in taking an allergy test should stop taking antihistamines several days before.

A week before conducting a test, it’s best to stop taking most antihistamines, even if they are prescribed by a doctor or other medical professional. With antihistamines such as hydroxyzine or diphenhydramine — over the counter options — you should stop taking them 10 days and 48 hours away from the test, respectively.

Do antihistamines affect all allergy tests?

The good news is that if you opt for a blood or hair sample test instead of the classic skin prick test, you often won’t need to have the same concern about your antihistamines. This is because these drugs only counteract redness and swelling of the skin (which is what the skin prick test deliberately causes). They won’t have any negative reaction to other testing methods.

However, it’s important always to follow the instructions of your family doctor or other professional that is going to be conducting the test. If they give you certain instructions for stopping antihistamines (or other drugs that you are taking), it’s to make sure that the test results are as accurate as possible.

While there’s nothing fun about taking an allergy test, there’s no question that it’s better to do it right the first time, rather than repeating it numerous times. Allergy tests and antihistamines have an important relationship to keep in mind. The more you know, the more accurate the results are going to be.