Keji's scarf, which has been used for two years, turns yellow, which is caused by skin allergy, infection and malnutrition. Ke Jiquan's skin and hair are usually red, black and bicolor. The scarf turns yellow, indicating that there is something wrong with the skin. Dog skin allergies can cause itching, redness, depilation and other phenomena, and some dogs will cause the skin to turn yellow during licking and biting; Part of the dog's collar is infected, which will cause the collar to turn yellow. Dogs are malnourished and lack essential nutrition, which also causes yellow hair and skin problems.