Sebaceous grains are generally known as cornu rashes in medicine, and their causes are mostly related to heredity, trauma, dermatologic diseases, and medications. 1. Genetic factors: cornu rashes may be related to genetic factors, usually from the neonatal period, by the undeveloped sebaceous glands or cuirasses funnels at the lower end of the epithelium. 2. Trauma: if the skin abrasions, burns and other traumatic injuries, it may trigger cornu rashes. 3. Skin disease: if the skin appears herpetic epidermolysis bullosa, follicular mucinosis and herpes zoster and other skin diseases, the skin lesions may be triggered by the recovery of localized cornu rashes. 4. Drugs: if the patient’s skin localized drug treatment, such as hormone drugs, etc., in the skin lesions may appear after the restoration of cornu rashes. There are many causes of cornu rashes, it is recommended that patients go to the regular hospital for examination, to clarify the cause, and follow the doctor’s instructions for treatment.