Genetically modified organisms (GMO) are used widely in food industry ever since last 20 years and took part in our lives widely nowadays. Transgenic foods were produced as a solution for food requirement of increasing world population. Only little data is known about GMO and also most discussions are surely about the effects on human health. Potential impacts for human health are oncogenicity, antibiotic resistance and development of allergy. On the other hand it is used for producing hypoallergenic infant formulas in and for oral vaccine production. An allergic protein is transferred into another food for acquiring transgenic organisms and by this procedure allergic reactions to unpredictible foods could be observed. Although GMO defenders claim transgenic foods are not much allergenic than natural foods; much more investigations are needed for assessing allergenicity of modified foods. Anahtar Kelimeler : genetiği değiştirilmiş organizmalar (GDO), alerji, transgenik besin.