It's best to avoid close contact with chemicals when you're expecting a baby. Usually the ban on hair dye is due to several reasons: 1. The woman and the fetus can be harmed by the chemicals that make up the dye, for example, ammonia, hydrogen peroxide, paraphenylenediamine, and resorcinol. 2. The condition of a pregnant woman can be affected by an unpleasant odor that most paints have. It can provoke nausea and vomiting, especially in the first trimester. 3. Due to hormonal fluctuations, the structure and oiliness of the hair change, and you can get a completely unexpected shade.