Hair Dye Effects on the Hair Coat and the Skin of the Dog: A Scanning Electron Microscopic Study

Eight healthy dogs of mixed breeds with short hair coats were used in this study. The skin and the hair of a small area on the left side of the saddle region were dyed 80 times once every day with a permanent hair dye, Clairol Hair Dye Flaxen Blonde. The dyed regions were red and dry toward the last two weeks of the experiment. None of the dogs had abnormal hair shedding. Four of the dogs were restless, and their epidermis were parakeratotic and hyperkeratotic.
The cuticular cells of the hair shafts of two dogs upon examination showed deep fractures at the lower part of the hair shaft. The fractures extended through the whole thickness of the cuticular cells leading to splitting of the hair shaft. Secondary hairs showed excessive peeling of their cuticle cells causing distortion and deterioration of the cortex of the hair. Cuticular cells of large numbers of hairs lost their apical parts and some of them were deformed due to partial dissolution attributed to the intensive use of the hair dye. The intensive usage of the hair dye on the compound type of hair coat of the dog caused damage to the hair shafts and to the skin in the form of irritation, dryness and parakeratosis of the epidermis. Also, some of the dogs became restless and hyperactive during the later part of the experiment.