The reasons for the increase in dandruff after hair dyeing are as follows: 1. Hair dyeing can easily cause fungal or bacterial infections, and you need to go to the clinic to do fungal immunofluorescence examination to rule out whether the increase in dandruff and hair loss is caused by fungal infections. 2. The presence of seborrheic dermatitis in oneself can stimulate the outbreak of seborrheic dermatitis through hair dyeing, and seborrheic dermatitis can lead to repeated itching of the scalp, the shedding of large pieces of dandruff, the increase in dandruff 3, too long hair dyeing or too high frequency of hair dyeing will stimulate the reaction of the scalp, which will lead to an increase in dandruff. 4, some patients are allergic to hair dyes, most of which are chemical substances, and after hair dyeing, sweat impregnation and the combined influence of the environment lead to hypersensitivity reactions of hair dyes to the scalp, stimulating increased dandruff, increased itchiness, and in severe cases, oozing and Folliculitis, etc.