Teenagers with less hair may be caused by staying up late, diet and nutritional deficiencies, but also due to head skin diseases, such as seborrheic dermatitis, tinea capitis, the main thing is to take the general treatment, drug treatment. 1. Stay up late: long-term stay up late will lead to endocrine disorders, hormone levels are abnormal, which leads to hair loss, must develop a good routine, go to bed early and get up early, avoid staying up late. 2. Nutritional deficiencies: If the body lacks essential nutrients, it may also have a certain impact on the hair, the diet must pay attention to increase nutrition, especially eat more food rich in protein, calcium, iron and other nutrients. 3. Seborrheic dermatitis: a chronic inflammatory skin disease, may lead to hair loss phenomenon, mainly to regulate the diet, avoid eating spicy and greasy food, at the same time with the local drug treatment, such as mometasone furoate cream, dinexidine cream. 4. Tinea capitis: mainly because of fungal infections caused by local use of antifungal drugs, such as ketoconazole cream, fluconazole cream, etc., if the condition is more serious, with oral antifungal drugs, such as itraconazole capsules, terbinafine tablets and so on. Teenagers with low hair volume if caused by skin diseases, must promptly go to the hospital, with the doctor to take treatment. If you need to use medication, you must be guided by a doctor and not use medication on your own.