Summary: Drug allergies are hypersensitivity reactions caused by immunological mechanisms involving drug-specific antibodies or T cells. Based on the time from drug exposure to the onset of symptoms, they can be divided into immediate and non-immediate reactions. The drugs that most often cause allergic reactions are beta-lactam antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs). In the vast majority of cases, skin symptoms predominate, but one should remember about the possibility of severe, life-threatening reactions, including anaphylaxis. Both in vitro and in vivo tests are used in diagnostics, and drug challenges are considered the gold standard of diagnostics. The primary goal of the drug challenge is to select safe medicinal products for the patient. The most important therapeutic treatment in the event of an allergic reaction is to discontinue exposure to the drug. Further actions depend on the clinical picture and may include pharmacotherapy, including the use of antihistamines and steroids. A special therapeutic method is desensitization. It is based on the creation of temporary tolerance to a given drug and its maintenance by systematic supply of this drug, however, due to the availability of alternative medicinal products on the market, it is rarely used.