Physical and Chemical Damage of Hair

Hair disorders associated with hair loss are discussed in Hair Loss and Its Causes. This section discusses disorders of the hair shaft.

Hair shaft abnormalities that are not genetic are due primarily to "weathering"-physical or chemical damage to the hair.

All scalp hair undergoes some degree of physical and/or chemical damage in the 2 to 8 years of its growth. Physical and chemical stresses damage the cuticle (outer, protective layer) of the hair shaft (see Hair as a Biological Fiber). Physical damage typically is associated with stresses such as:

• long-term braiding or corn-rowing,
• hard brushing and combing,
• permanent waving, and
• excessive exposure to ultraviolet radiation in sunlight.

Chemical damage typically is associated with:

• bleaching,
• dyeing,
• use of chemical straighteners,
• curling and waving chemicals, and
• excessive exposure to salt water and ultraviolet radiation ("surfer's hair").

Long-term physical and/or chemical stresses can result in chronic problems of hair styling and management: hair breakage, hair "frizz", and broken or "paint-brush" hair tips. Over the 2 to 8 years of its existence, a hair shaft is likely to suffer damage from even normal activities of combing and brushing, wetting and drying, coloring and styling, but this does not usually cause severe hair damage.

Severe physical and/or chemical damage usually can be prevented by avoiding abnormal physical and chemical stresses. Severe physical and chemical damage to the hair shaft cannot be undone; however, cessation of harsh stresses can prevent further damage. Proprietary products are available to minimize "frizziness" and restore hair pliability. See Keeping Our Hair and Scalp Healthy for more information.