Another causes for dandruff is when your scalp is sensitive to hair products. Some cleansers might have a lot of chemicals. The harsh cleansers in many shampoos can wash away the scalp's acid mantel (which is the natural acidity that protects your skin) leaving it susceptible to dryness and irritation.Sometimes sensitivities to certain ingredients in hair care products or hair dyes, especially paraphenylenediamine, can cause a red, itchy, scaly scalp. Shampooing too often or using too many styling products also may irritate your scalp, causing dandruff.