What types of allergies are there—and why you shouldn’t take medication before the test

9. Juni 2025 ca. 5 Minuten

Are you suffering from a rash, itching, or watery eyes and suspect you have an allergy? An allergy test is the right way to get clarity. But many people don’t know that if you have taken antihistamines beforehand, the test may be inaccurate under certain circumstances. In this article, we explain why, how to prepare properly, and what to do if you have an allergic reaction.

What types of allergies are there?

Allergies are widespread, but they often manifest in very different ways. Some people react to pollen with sneezing and watery eyes, while others develop an allergic rash after eating certain foods. In others, pet dander or dust triggers breathing difficulties. Insect venom, medications, or contact allergens such as nickel can also cause allergies. Symptoms range from mild discomfort to severe, life-threatening reactions.

Why is an allergy test important?

An allergy test helps you find out which substances irritate your body. Only once you know what you are allergic to can you take steps to avoid it, prevent reactions, or start appropriate treatment. There are various testing methods, from traditional skin tests to modern blood tests, but good preparation is essential for all of them.

How do antihistamines work—and why can they affect the test?

Antihistamines are medications that many allergy sufferers take in their daily lives. They block the effects of histamine, a substance produced by the body that is released during allergic reactions. However, the very effects they suppress—such as redness, swelling, or itching—are deliberately triggered during an allergy test to make a reaction visible.

So, if you have taken antihistamines shortly before the test, your body may show little or no reaction - even if you have an allergy. This means: The test shows a negative result even though you are actually allergic.

Not all tests are equally susceptible to distorted results:

How long should you stop taking antihistamines before an allergy test?

To ensure the test results can be reliably assessed, you should pause antihistamines a few days before the test. The exact duration depends on the active ingredient. As a rule, for common medications such as cetirizine or loratadine, an interval of 3 to 5 days is enough. For long-acting medications such as desloratadine or fexofenadine, you should stop taking them about 7 days beforehand.

If you're unsure, be sure to talk to your doctor or the practice carrying out the test. Other medications, such as creams or tablets containing cortisone, can also affect the results and should be discussed with a doctor beforehand.

Do I also need to stop taking antihistamines before an allergy blood test?

The pause applies to the skin test. In its guidelines on allergy testing in the laboratory (in-vitro allergy diagnostics, as of 2010), the German Society for Allergology and Clinical Immunology (DGAKI) lists the use of antihistamines as a contraindication for skin testing. In this case, it recommends measuring specific IgE in the blood before the skin test, that is, antibodies against a specific allergy trigger (paraphrased from DGAKI, 2010).

The difference lies in what is measured. The skin test shows whether your skin reacts visibly, and antihistamines can weaken that exact reaction. The blood test, on the other hand, measures antibodies in the blood sample.

The guideline describes blood testing at the doctor's office; it says nothing about at-home tests. For home use, mybody®x (MYBODY Lab GmbH) offers the AllergoCheck: It measures IgE antibodies to 54 of the most common allergens from pollen, house dust, animal hair and foods; a finger prick is all that is needed for the sample. Ask your doctor or pharmacist beforehand whether you can continue taking your antihistamines before this test. An IgE level indicates sensitization, not a diagnosis. Sensitized means that measurable antibodies are present - some people have them and never react. Whether this develops into an allergy depends on symptoms, and that is for a doctor to assess.

What to do in the event of an allergic reaction?

If you experience an acute allergic reaction regardless of the test, it is important to act quickly. Early signs can include itching, skin redness, hives, difficulty breathing or circulatory problems. In such cases:

• If possible, remove the trigger (e.g. a food or contact allergen)

• Sit down calmly and stay relaxed

• Take an antihistamine (if prescribed)

• For severe reactions or difficulty breathing: call emergency services (112) immediately

People with known severe allergies are advised to carry an allergy emergency kit with an adrenaline pen.

Conclusion: Good preparation leads to clear results

If you want to know which allergies you really have, an allergy test is a sensible step. However, for the test to be meaningful, you should not take antihistamines beforehand - and ideally consult a doctor or pharmacist.

mybody®x helps you understand your body better

At mybody®x, we offer modern health analyses and at-home tests - for example, for food intolerances, microbiome analysis or checking your nutrient status.

👉 Find out more: www.mybody-x.com