Careful blow drying on a moderate setting should not damage the hair - but if this dryer is set on maximum heat it may be too close to the hair

Some of the tools of the hairdresser's trade - notice the broad brushes, which are 'kind' to the hair

Damage from hair treatments

Shampooing should not in itself damage the hair, since modern shampoos do not lift the cuticle. In the past, when harsh shampoos were often used, acute and irreversible tangling or matting sometimes followed shampooing. The culprits were usually antiseptic shampoos, and they could turn hair into a mass that looked more like sheep's wool than human hair.
    This kind of matting is seldom seen nowadays, fortunately, since most modern shampoos contain conditioning agents and help to protect hair. Small amounts of tangling and occasionally matting are still quite common, however, especially in long weathered hair. It generally affects only small locks of hair or even a few adjacent hairs. It may be the result of wetting and drying hair without shampoo, since friction is higher in wet hair than in dry. It can happen when the hair is piled up on top of the head for shampooing -a recipe for tangling if ever there was one.
    Of the common cosmetic procedures, permanent waving, bleaching and dyeing all damage the hair to some extent. Permanent

Repeated bleaching and perming will significantly affect the hair's porosity and make it vulnerable to further damage