(Don't actually use nut shells.)
Exfoliation is the process of removing the top layer of dead skin cells. The body naturally sheds some of these dead cells by itself, but as we age the cycle of new cells to dead cells slows down. As a teen it can be as short as 15 days, and by 70 it could take a few months. Speeding up this cycle (known as desquamation) is vital to keeping skin young and healthy.
Using moisturizer on dead skin cells is ineffective. In order to properly moisturize, product needs to be applied to live cells. Often people with dry skin tend to gravitate towards heavier and heavier moisturizers, not realizing that the dryness they feel is the layer of dead skin preventing their moisturizer from absorbing.
Physical exfoliation refers to manual scrubbing. This is created by some sort of grit in the product, whether sugar, salt, microbeads, ground up shells (avoid at all costs), sand, or various other additives. The smaller the particles, the stronger the exfoliation. Microdermabrasion is also a form of physical exfoliation, where tiny crystals are applied and removed with suction. Using a facial brush is also a form of physical exfoliation. Physical exfoliation is great for flakiness and dullness on healthy skin. Physical exfoliation should not be used on sensitive skin, rosacea, inflamed acne or eczema.
Whichever type of grit is in the product should be accompanied by a lubricant to decrease friction. Manual scrubbing can be very irritating, especially if done too often. Over scrubbing can cause inflammation, which is an underlying cause of most skin conditions.
Chemical exfoliation refers to using a chemical, usually an acid, to dissolve dead skin cells. This is generally more effective than physical exfoliation, since dead skin cells can be both on the surface of the skin as well as lining the pore wall, where grit is too large to reach. Generally these chemicals are not actually "peeled" off the face.
There are alpha and beta hydroxy acids. AHAs are better for treating aging skin since they penetrate deeper. BHAs are better for acne. Glycolic, salicylic, and lactic acids are all very common. The best acid for exfoliation depends on skin type and condition.
Enzymes are another variant of chemical exfoliation, generally derived from plants such as pineapple and papaya. These enzymes "eat" dead skin cells instead of dissolving them.
Chemical peels given in a spa or dermatologists office are much stronger than chemical exfoliants available for purchase by a customer. The stronger the percentage of active ingredient and the more acidic the peel, the deeper into the skin it penetrates. Peels are extremely effective at treating acne, fine lines, hyperpigmentation, wrinkles and other signs of age.
Just like scrubs, peels come with risks. Peels that are too strong can cause chemical burns, which can result in hyperpigmentation and scarring. Peeling too often can cause sensitivity as well. Going to an esthetician, dermatologist or plastic surgeon that has knowledge and experience with peels is extremely important. When in doubt, err on the side of caution.
Always follow exfoliation with moisture. This is the prime opportunity for serums and moisturizers to penetrate deepest into the skin, making them more effective.
Fresh skin cells are more sensitive to sun damage than dead skin cells. Avoid the sun after exfoliating and wear SPF 30 or higher sun protection. If you get sun exposure after a deep exfoliation, the risk for hyperpigmentation is very high.
How often you should exfoliate depends on your skin type and condition, and really should be determined by your esthetician after a skin analysis. As a general guideline, two times a week is a good average. Also ask your esthetician what kind of exfoliation is best for your skin. Everyone's skin is unique and has vastly different needs.
What do you use to exfoliate? Post in the comments below.