1. Malnutrition: It is related to microelement deficiency, hair nutrient deficiency and blood loss. With the improvement of living standards, dystrophic alopecia is rare;

2. Overnutrition: Obese teenagers will secrete too much oil, leading to seborrheic alopecia;

3, too much pressure: adolescents due to excessive learning pressure lead to kidney deficiency, lack of qi and blood, leading to hair loss.

Besides,

1. Genetic factors: Heredity is a common cause of androgenic alopecia. If there is hair loss in the family, then the probability of hair loss in the offspring is relatively high. Because of the strong androgen in the body, it acts on local hair follicles, which leads to the gradual atrophy of hair follicles and the symptoms of hair loss can appear.

2. Psychological factors: excessive mental stress or strong stimulation of alopecia is prone to alopecia areata or alopecia totalis.

3. Autoimmune factors: Long-term anxiety, tension or postpartum immune diseases are more likely to induce alopecia areata.

4. Infection: Being infected by virus or bacteria will damage hair follicles and form hair loss.

5. Scalp trauma: Trauma will stimulate the scalp, leading to the formation of scalp scar and cicatricial alopecia.

6. Long-term bad habits: For example, if the hair is involved too much or the hair is pulled too tightly, it is more prone to hair loss symptoms.