Abstract: In recent years,we found that calf sensitization occurred in large scale dairy farms,and the incidence rate of calf allergy was higher in cow's photosensitivity. After detailed investigation and analysis,most of the diseased calves are within 1 month old and still belong to the stage of breast milk. They occur in the area of non pigmented skin or hairless skin,showing pathological changes such as depilation,scaling,congestion,edema,exudation and scab. Before the photosensitive allergy of calves,they had diarrhea,high fever,asthma,pneumonia and other diseases or disease symptoms. They had used ceftiofur for injection,enrofloxacin injection,sulfonamides,oxytetracycline injection,gentamicin injection and other drugs,and had ultraviolet irradiation with appropriate wavelength. The final diagnosis was drug-induced photoallergy,also known as primary photoallergy. The specific reason is that the drug that can cause photoallergy is used,and the dosage is too large and the medication time is too long. Scientifically eliminate the causes of photosensitive allergy in calves,improve the level of scientific drug use in calves,and enhance the understanding of grass-roots veterinarians about the disease.

Key words: calves, photosensitive allergy, primary hypersensitivity, hepatogenic photoallergy