Don't scratch your scalp before dyeing your hair. Just rub your hair gently after washing it. Nutritionists can help. Hair dye will open hair scales and absorb nutrients better. There is also a skin test before dyeing hair, otherwise the allergy will be bad. The barber will do this for you, and you don't have to worry about anything else. As long as you don't scratch your scalp, there will be no problem.