wie lange vor allergietest keine antihistaminika — what does this mean exactly?

The question means: 'How long before an allergy test should you stop taking antihistamines?' – a common patient query before skin prick tests or specific IgE blood tests. Antihistamines block histamine receptors and can suppress the wheal-and-flare reaction in skin tests, leading to false negatives. The required washout period depends on the drug: short-acting antihistamines (e.g., cetirizine, loratadine) should be stopped 3–7 days before testing; long-acting ones (e.g., desloratadine, levocetirizine) 7–14 days. For nasal or ophthalmic antihistamines, 48 hours may suffice. Crucially, discontinuation must be discussed with a physician, as some patients may experience rebound symptoms or worsening of their condition. The evidence is based on clinical practice guidelines (e.g., EAACI) and expert consensus, not large randomized trials. The test is not a DNA test but a functional or serological allergy assessment. Caveat: In severe allergy or asthma, stopping antihistamines should only be done under medical supervision.