There is no certain rule as to how old a woman usually grows gray hair, and a person can grow gray hair at any time in his or her life. The growth of gray hair is affected by a combination of genetic factors, lifestyle, and disease factors. 1. Genetic factors: If a close family member has early gray hair, then the possibility of other members of the family having early gray hair rises. 2. Lifestyle: irregular work and rest, getting up early and staying up late; work pressure, mental anxiety, etc. are prone to premature gray hair. 3. Disease factors: systemic nutritional deficiencies, vitamin and mineral deficiencies are prone to gray hair; skin problems such as vitiligo will also appear gray hair. If a woman has premature gray hair, you need to get a medical checkup, and take the right treatment after finding the problem as soon as possible.