Suddenly a lot of dandruff may be caused by contact dermatitis, seborrheic dermatitis, psoriasis and other reasons. 1. Contact dermatitis: the use of irritating shampoos, perms or hair dyes can induce contact dermatitis, which can severely irritate the scalp, causing a sudden increase in dandruff, which may be accompanied by itching and stinging symptoms. 2. Seborrheic dermatitis: it may be related to genetic factors and environmental factors, and when it appears in the scalp area, it will increase dandruff in the scalp area, which may be accompanied by itching, erythema and other symptoms. 3. Psoriasis: this disease belongs to a kind of immune skin disease, mostly considered to be related to genetic factors, which can lead to the appearance of erythematous spots or plaques on the skin of the affected area, covered with silvery-white scales, and it is common in the head, the extensor surface of the limbs, and the torso, which can make dandruff increase. Suddenly a lot of dandruff, if accompanied by other uncomfortable symptoms, should be taken seriously, as soon as possible to seek medical attention. After diagnosing the cause of the disease, the doctor will guide the treatment.