Food allergy is most often linked to the type I allergic reaction, while IgE-dependent mechanism causes symptoms in only about 50% of patients. If symptoms are coming from other types of allergic reactions we do not have enough standardized diagnostic methods. The purpose of our review is to discuss the possibilities of diagnosis of food allergies. Regardless of the causal mechanism the interview has the most important role in the diagnosis, and the gold standard is a double blind placebo controlled food challenge. Additional tests that can be performed in suspected IgE-mediated reactions include: skin prick tests, specific IgE measurement, component-resolved diagnostics and in doubtful cases basophil activation test (BAT). Due to the fact that the spectrum of the symptoms of the type I food hypersensitivity can include potentially life-threatening reactions, diagnosis is often limited to in vitro assays. In these cases BAT may play an important role--in a recent publication, for the first time BAT reactivity reflected the allergy severity and BAT sensitivity reflected the threshold of response to allergen in an oral food challenge. Atopy patch tests are valuable diagnostic tool in suspected type IV food hypersensitivity, but due to the lack of standardization they are not used routinely. The cytotoxic test has been developed on the basis of the observations that leucopenia developing in the type II hypersensitivity reaction mechanism may be one of the symptoms of food allergy. Unfortunately its use is not justified in any method fulfill the criteria of controlled clinical trial. Food allergy can also develop in the type III hypersensitivity reaction, but there is lack of research supporting the role of IgG measurement in the detection of allergens responsible for symptoms. Each result of additional diagnostic tests before the introduction of food elimination should be confirmed in double-blind, placebo-controlled or open food challenge, because non proper diet is not only ineffective but also can be harmful.