What types of allergies exist – and why you shouldn't take any medication before the test.

Are you suffering from a rash, itching, or watery eyes and suspect an allergy? Then an allergy test is the right way to get clarity. But many people don't know: If you've taken antihistamines beforehand, the test results can sometimes be inaccurate . In this article, we'll explain why this is the case, how to best prepare , and what to do in case of allergic reactions .

What types of allergies are there?

Allergies are widespread – but they often manifest themselves in very different ways. Some people react to pollen with sneezing and watery eyes, others develop an allergic rash after eating certain foods, while for still others , pet dander or house dust triggers respiratory problems. Insect venom, medications, or contact substances like 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 when you know what you're allergic to can you specifically avoid it, take preventative measures, or start appropriate treatment. There are various testing methods – from the classic skin test to the modern blood test – but good preparation is crucial for all of them.

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

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

If you took antihistamines shortly before the test, your body may not react at all or only minimally – even if you have an allergy. This means the test will show a negative result even though you are actually allergic.

Not all tests are equally susceptible to falsification:

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

To ensure a reliable test result, you should stop taking antihistamines a few days before the test . The exact duration depends on the active ingredient. Generally, for common medications like cetirizine or loratadine, a break of 3 to 5 days is sufficient. For long-acting preparations like desloratadine or fexofenadine, you should stop taking them at least 7 days beforehand.

If you are unsure, definitely speak to your doctor or the clinic performing the procedure. Other medications – such as cortisone creams or tablets – can also affect the results and should be discussed with a doctor beforehand.

What to do in case of an allergic reaction.

Should you experience an acute allergic reaction , regardless of the test, quick action is important. Early signs can include itching, skin redness, hives, shortness of breath, or circulatory problems. In such cases:

• Remove the trigger if possible (e.g., a food or contact substance).

• Sit down and stay relaxed.

• Take an antihistamine (if prescribed).

• In case of severe reactions or shortness of breath: call emergency services (112) immediately.

People with known severe allergies are advised to carry an allergy emergency kit with an adrenaline auto-injector.

Conclusion: Good preparation leads to clear results

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

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