Why are Acids Used in Chemical Peels?
Skin care is one of those fields that is full of crackpot ingredients (and incredibly overpriced ones), but the acids used by Skin Laboratory are among the few ingredients that are actually up to something.
All of our chemical peels use at least some form of acid. These acids belong to one of two categories: Alpha-Hydroxy Acids (AHA) or Beta-Hydroxy Acids (BHA).
[sws_divider_small_padding][accordion auto_height="true" ui_theme="ui-start" collapsible="1" active="true"][accordion_panel title="Highly Technical"]A number of carboxylic acids are used as cosmetics. Familiar to many readers is glycolic acid. It’s used in over-the-counter “cosmeceuticals” to improve skin tone. Also used in professional “chemical peels” is trichloroacetic acid. These acids are all closely related to the familiar acetic acid, but they have “electronegative” substituents.
In the aqueous systems we’re talking about, the strength of an acid is related to its tendency to liberate protons. An acid’s tendency to dissociate into protons is related to the thermodynamic stability of its “conjugate base” – the acid, minus a proton. These electronegative substituents withdraw some electron density from the negative charge on the conjugate base, giving a more potent acid.
This is one part of how these compounds seem to work; these mild acids help slough off dead skin cells, revealing the smoother skin underneath. Trichloroacetic acid is much stronger than acetic or even glycolic acid, and is, thus, only used by professionals.
Salicylic acid is another acid used in skin care; its hydroxyl group likely helps stabilize the conjugate base by virtue of its electronegativity alone, but it also can participate in a “hydrogen bond” (to a first approximation, the sharing of a proton between two electronegative atoms – usually oxygen, nitrogen, or fluorine). This gives a good energetic “bonus,” stabilizing the conjugate base, salicylicate.
Beta Hydroxy Acids (Salicylic Acid)
These acids are oil soluble, thus making these acids perfect for oily/acne skin that needs deep pore cleansing and loosening of blackheads. Beta-Hydroxy Acids (BHAs) can be used as a “first-step” before using Alpha-Hydroxy Acid (AHAs) peels to remove all oils from the skin, or use along 3/4 times per week for oil/blackhead control. A beta-hydroxy, this acid penetrates the upper layers of the epidermis only.
BHAs are excellent chemical exfoliants. They are an intense variety of exfoliant for the face that work by breaking up and shedding the outermost layers of the skin to reveal younger, healthier skin beneath. It can help reduce the appearance of fine lines, wrinkles, acne scars and may improve mild skin discoloration.
It is very important to note that chemical peels, while perfectly safe, are NOT for everyone. Because they involve the application of strong chemicals to delicate facial skin certain people should avoid using these products, namely those with active acne, sensitive and/or fragile skin. Also note that chemical peels are best suited for those with light to medium skin, and less suited for dark skin. If you have any doubts about whether a chemical peel is right for you, consult your dermatologist.
Alpha Hydroxy Acids (Glycolic and Lactic Acid)
AHA (Alpha Hydroxy Acid) is a collective name given to a group of fruit acids. The more common of the AHAs are glycolic (in sugar cane), citric (in citrus fruit) and tartaric (in grapes). They are used to exfoliate the skin chemically.
What are AHA’s and How do They Work?
The Alpha Hydroxy acid is known for its anti-aging effects and the fact that it is not toxic to skin. AHA acids are derived from fruits and flowers that help in making skin smoother and look healthier. Alpha hydroxy acids are naturally occurring acids like lactic acid from sour milk; citric acid from citrus fruits like oranges and lemons; and glycolic acid from sugar cane.
The most common AHA is glycolic acid. Being small, it is absorbed well by the skin. It promotes the skin to be more regular in its inevitable progression from the bottom layers to the top. Connections (desmosomes) to other cells are stronger. Deeper in the dermis, collagen is stimulated. The result is a smoother skin, with a better luster and less pigmentation.
Alpha Hydroxy Acids (AHA’s) work by releasing the “intracellular glue” which hold skin cells together, allowing the newly released cells to “slough off”. This activity stimulates or speeds up the cellular turnover process, which naturally slows down as we age.
In addition, glycolic acid, the most popular AHA, has a low molecular weight that allows it to penetrate deeply in the skin and stimulate collagen production.
AHA for Skin Exfoliation
Low-concentration alpha hydroxy acids (AHAs) and salicylic acid (called cosmetic acids) are chemicals promoted to improve signs of photo-aging such as rough skin surface texture, fine lines, and uneven pigmentation. Home use of cosmetic acids originally became popular because they provide quick results on areas of rough skin by peeling off or exfoliating the upper layers of the epidermis, exposing smoother skin underneath.
Unlike physical exfoliates that removes debris through gentle abrasion, hydroxy acid-based exfoliants smooth the skin by dissolving the intercellular “glue” that attaches the cells to the surface.
Glycolic is the most widely used because of its small molecular structure which slips beneath the outer layers of skin to stimulate collagen growth. Lactic Acid, because of its humectants property, tends to be most beneficial for dry/aging skin. Salicylic acid, a BHA which is most beneficial for oily/acne prone skin, are very powerful as well and should be used accordingly.
AHA’s are one of the safest methods of skin renewal. Their effectiveness depends on the type and concentration of the AHA, its pH (acidity), and other ingredients in the product.
In formulating our products for the face, we wanted to create a peel treatment that would not be irritating to the skin. For this reason we could not use the alcohol which is usually used.
Instead we dissolve the acids in a gelled environment of propylene glycol. This is quite a bit more expensive, but it allows us to create something that can be left on the face for a much longer time, without sacrificing the product’s strength.