Allergy to wheat proteins is the most common type of occupational asthma caused by cereals. Its incidence based on international reports is about 1-2.4/1000 cases among workers per year. In Mexico there is an underdiagnosis of occupational asthma > 99%. During the period 2009-2012 we recorded 5 cases of occupational asthma, 40% of them caused by cereals. This is the case of a 38 year old male, baker for 24 years exposed to wheat flour. In his workplace he used to wear surgical mask and there are no exhaust fans. He initiated 10 years ago with sneezing, itching, hyaline rhinorrhea and nasal obstruction. The following year he presented mild to moderate dyspnea, chest tightness, cough and wheezing during working hours, which improved during his days off. Pulmonary function tests were confirmatory of asthma, with negative skin prick tests to aeroallergens. Specific bronchial challenge was performed with wheat flour resulting positive with a decrease in VEF1 greater than 20%. Pharmacological treatment was provided and was sent to occupational medicine service for evaluation. The case was qualified as an occupational disease with a permanent partial disability of 25%, receiving a financial compensation. He returned to work in the same company but in a different area without wheat flour exposure. The diagnosis of occupational asthma is mainly clinical, according to Brooks¥ criteria, and a bronchial positive challenge test will confirms the diagnosis.