Baker's asthma, like other forms of occupational asthma is probably the most serious manifestation of occupational allergy among bakery workers. It is caused by immunologic sensitization and subsequent allergic reactions in the airways to occupational specific airborne allergens. Skin Prick Tests (SPTs) play an important role in the diagnosis of baker's asthma and epidemiological field studies on frequencies of sensitization to flour. This paper presents a review of the available literature on prevalence of flours sensitization in bakery workers. Atopy and level of exposure appears to be a very strong determinant for sensitization to flour allergens. Prevention strategies and standard setting are discussed.