It is not recommended to dye hair during physiological period, some women have symptoms such as menstrual cramps, diarrhea and low immunity during physiological period, stimulation by hair dyes can easily lead to skin allergies, and dyeing hair for a long time can easily induce colds, etc. It is better to dye hair after physiological period. Dyeing hair during physiological period may lead to the following adverse reactions. 1. Skin allergy: If you dye your hair during physiological period, the various chemicals in the hair dye can easily cause skin allergy, resulting in rashes, itchy skin, redness and other adverse reactions. 2. Induce colds: Hair coloring takes a long time, the scalp is in a humid state, easy to induce colds. If skin allergy occurs during the physiological period of hair coloring, you need to go to the hospital in time to avoid delaying the condition.