Understanding Aging Hair

Dermatologists are frequently consulted for evaluations of hair thinning by both men and women; however, they should think beyond hair thinning and understand the physiology of aging hair. Changes in the hair shaft itself with maturity are worth understanding, as they provide the data necessary to develop a clinical plan to address hair loss in a more holistic fashion. What happens to hair as it ages?

It is well established that hair grays with maturity, and the number of hair fibers decreases. The diameter of the hair fiber also decreases with advancing age. The hair shaft diameter decreases after puberty for men and after age 40 in women. This is important because chemical processing, such as permanent hair dyeing and permanent hair waving, must penetrate the hair shaft to have the desired effect. If the hair shaft is thinner, the chemicals will enter the hair shaft more quickly, meaning the length of time the permanent hair dye or the permanent wave solution remains in contact with the hair is shortened. If the chemicals remain in contact with the hair too long, permanent hair shaft damage due to structural weakness could occur. The resulting hair breakage will contribute significantly to the preexisting hair thinning.

Other age-related changes are also present. The lipid coating on the hair decreases, especially in women, with the onset of menopause. This creates the need for conditioners. Instant conditioners can be applied to freshly shampooed hair in the shower and then rinsed. They contain dimethicone and quaternary ammonium compounds designed to leave a thin coating on hair shafts that reduces friction, reduces the effects of static electricity, and adds shine. Friction between hair shafts is the main cause of hair breakage during combing, brushing, and styling. Instant conditioners can be augmented with leave-in conditioners applied to towel-dried hair outside the shower and left in until removed during the next shampoo. The formulations are similar between instant and leave-in conditioners. The thin film coating on each hair shaft mimics, but does not replace, the hair lipids.

Hair curvature also increases with aging, preventing the hair from lying flat. When hairs lie in many different directions rather than being orderly and smooth, hair luster decreases. Hair luster is also decreased due to the lifting of the hair cuticle. A tightly overlapping hair cuticle is necessary for hair strength, as the cortex and medulla offer little structural support. It is the light reflected from the smooth, overlapping cuticular scales that creates the appearance of hair luster. Defects in the overlapping cuticular scale can be minimized by using silicone, argan oil, and other vegetable oil–based hair oils. The hair oil is pumped into the hands and finger-combed through the hair. Dimethicone is usually the preferred silicone, as it is hypoallergenic and noncomedogenic. It can smooth the cuticle, relax some of the curl, and reduce static electricity that causes frizzy hair. The oil can be applied to dry hair daily and has a lubricating effect on hair shafts, thereby reducing traumatic hair breakage from combing and brushing. The oil also adds shine to the hair surface.

The aging hair shaft also becomes more structurally inhomogeneous with a porous medulla, which contributes to weakening and increased breakage. This means the hair should be handled gently, like a silk scarf—no pulling, yanking, or aggressive combing or brushing. The hair should not be combed when wet, as it becomes more elastic and prone to breakage. In short, aging hair should be manipulated and exposed to chemical procedures as little as possible, with aggressive use of conditioning agents. This will optimize hair performance and appearance, especially in the presence of thinning hair.