Exfoliation is a technique where the layer of mostly dead epidermal cells on the outer surface of the skin (a.k.a. stratum corneum) is removed to expose fresher mostly living cells. Potential benefits of exfoliation include fresher, brighter looking skin, better penetration of active ingredients of skin care products and, for people with excessively oily skin, a varying degree of reduction in oil secretion.
It is debatable whether exfoliation reduces file lines, but it generally does not improve significant wrinkles since its effects do not reach the dermis where wrinkles are formed.
Routine exfoliation should not be confused with deep chemical peels, laser peels and other semi-invasive wrinkle treatments methods. The idea of such methods is not to strip the dead cells from the epidermis (as routine exfoliation does) but to create controlled trauma to the dermis, the deeper layer responsible for structural integrity of the skin. The subsequent wound-healing response and skin remodeling help to wipe out some of the wrinkles. Procedures like deep chemical peels are aggressive treatments to be done infrequently by trained professionals. Their mechanism of action is different -- they are not simply intense versions of routine exfoliation.
Now that the terms are clear: Is routine exfoliation beneficial and who can benefit? The benefits of adding exfoliation to a skin care routine are not universal. First, the skin undergoes continuous natural exfoliation anyway. If it weren't, the skin would be inches think because continuously produced new epidermal cells (keratinocytes) would accumulate. Epidermal cell turnover and the resulting natural exfoliation are more rapid at a young age. Therefore, young people generally do not benefit from exfoliation and are more likely to suffer its side effects. Even some people in their 30-s and 40-s have naturally high cell turnover and may not benefit from routine exfoliation. On the other hand, many people over thirty develop dull, lifeless looking skin because their stratum corneum (topmost layer consisting of dead cells) becomes too thick. This group is likely to benefit from routine exfoliation. Since exfoliation sometimes reduces the production of skin oil (sebum) people with excessively oily skin may benefit too, especially if they exfoliate with beta and/or alpha hydroxy acids. On the other hand, exfoliation may cause further irritation in people with dry and/or sensitive skin, who should either refrain from exfoliation or use mild exfoliants infrequently.
If you decided that exfoliation should be a regular element of your skin care routine, how often should you do it? Except for people with extremely oily skin, daily exfoliation is not a good idea. You goal is to remove the dead cells from the skin surface. It takes at least a few days for a sizeable amount of dead cells to accumulate. If you exfoliate more often than that, you may be removing too many living cell, increasing the chance of irritation and skin damage.
For most people who decide to exfoliate, once or twice a week is sufficient. You should determine optimal frequency based on your skin type, strength of the exfoliants you use, application technique and other factors. If you develop irritation, increased sensitivity or dryness, you are probably exfoliating too much.
Popular exfoliation methods include alpha and beta hydroxy acids, enzyme peels, microdermabrasion and others. Some may have collateral benefits. For example, alpha-hydroxy acids (especially glycolic and lactic) seem to have additional skin benefits independently of their exfoliating effect, such as improvement of dermal matrix. Beta-hydroxy acids, such as salicylic acid, are particularly effective in reducing excess oil production and may be a good fit for oily, acne-prone skin. On the other hand, chronic irritation and skin damage from overuse of acidic exfoliants is a known dermatological entity and may contribute to skin aging. Be prudent: listen to your skin, use common sense and inform yourself before trying anything new.
