A 40-year-old female farmer is described, with a rare coexistence of 4 different occupational diseases sharing one common cause: allergy to cow epithelium (Bos domesticus). First symptoms started after 6 years of working on the farm. The allergic diseases appeared in the following sequence: rhinitis, protein contact dermatitis, asthma, conjunctivitis, and finally contact urticaria. The time span between the first and the last allergic manifestation to develop was 9 years. By the time of examination, 4 shock organs (the upper and lower airway, conjunctivae and the skin) were involved. Skin prick tests with common aeroallergens, farm animals, pets, and agricultural dusts were all negative, total IgE was within normal range (90 kU/l). Intracutaneous test and bronchial provocation with cow epithelium allergens were both positive. Specific IgE was detected to cow dander (CAP class 3) but not to bovine serum albumin (CAP 0). A positive reaction to goat dander (i.c. positive, CAP 2) was interpreted as a cross reactivity, because the patient never had contact with goats. The article also reviews known sources of cow allergens and occupations at risk. Besides farmers and veterinary surgeons, also butchers, cheese makers, bakers, cooks, laboratory workers and even beauticians may be at risk for developing occupational allergy to cow allergens.