Hair that does not grow long may be caused by malnutrition, ringworm of the head, or scalp folliculitis. 1. Malnutrition: Due to dieting or insufficient intake of meat and other micronutrients, which cannot supply nutrients to the hair follicles, hair growth may not occur. 2. Ringworm of the scalp: It is caused by contact of the scalp with pathogenic dermatophytes, and is a common disease of the scalp. The common symptom is hair loss spots with scaling and hair breakage, which manifests itself as hair that doesn’t grow. 3. Scalp folliculitis: red papules are common, accompanied by the symptom of hair loosening and easy to pull out, and scarring with flaky hair loss can also occur. Mostly caused by bacterial infection, is a kind of inflammatory skin disease, the patient may appear the phenomenon of hair growth. There are many reasons that lead to hair not growing long, and it is recommended that patients go to the hospital in time to clarify the cause of the disease.