( 
)
By Hannah Sivak, PhD
Chemical peels: the basics.
A peel is a chemical solution that is applied to the skin and allowed to penetrate and wound it in a controlled way. Healing will follow, the old skin will peel and new skin will take its place.
The chemicals used are sometimes called exfoliating or wounding agents. Wounding is a good word for this, because depending on the method, the effect may be second degree burns and the pain so severe as to require general anesthesia.
Who can do a peel?
In chemical peels, a doctor, esthetician, or you, apply a chemical solution to your skin with the objective of destroying it, so that when your skin heals many of the previous visible defects will be gone.
What can go wrong?
The deeper the destruction, the more can go wrong. Some people may heal with scars, in others melanocytes may die leaving spots of hypo-pigmentation; a person with allergy to aspirin may have a bad reaction, etc. For people with “dormant” herpes virus, the peel may induce a re-awakening of the virus and reappearance of symptoms.
What can go right?
Old scars may go away, the same for minor wrinkles, age spots, etc. The deeper the destruction, the more can go right.
What are the options?
Type and concentration of the chemicals used, and how the solution is applied, these variables will determine the depth of the peel.
The chemicals used most frequently in peels are alpha hydroxy acids, trichloroacetic acid, salicylic acid and resorcinol. AHAs are used for superficial peels; TCA is more frequently used for medium peels.
Factors that may affect the depth of a peel include the concentration of the peeling agent, the number of coats that are applied, and the amount of time allowed before the acid is neutralized. Deeper peels result in more dramatic effects as well as higher risks, increased pain, and longer healing time.
Examples of alpha hydroxy acids are glycolic, malic, mandelic and lactic (others are used more for label value than for real value). AHAs differ in pK, which is a measure of the tendency to lose a proton. The higher the concentration of protons, the more acidic the solution will be and the lower the pH, so the lower the pK the stronger the peel will be. Another important factor is concentration: the higher the concentration of the acid, the more protons will be released into the water and the stronger the peel.
Tip: Another label trick used by manufacturers: use a high concentration of acid but add base (like sodium hydroxide) to convert protons into water. You can then have a high concentration of “acid” on the label but most of that acid would have been converted into salt: not much use in a peel but good for sales.
The pK of lactic and glycolic acids is very similar. Why is it then that glycolic peels are stronger than lactic peels at the same concentration? Nothing to do with penetration. The reason is that by using % (weight per volume of solution) we are comparing apples with oranges. This is not an effective way of comparing concentrations. Biochemists use molarity, which compares similar number of molecules. Because the glycolic molecule is smaller than lactic acid, the same weight of chemical will contain more molecules of glycolic acid than of lactic. In a solution this difference will translate into more protons.
TCA and salicylic acids are not alpha hydroxy acids, and they work not simply because of their acidity but through complex interactions with the skin proteins. TCA interacts with water molecules, exposing hydrophobic parts of the protein that would not be affected by the AHAs. TCA is used in concentrations between 25 and 50%, and because % can mean different things (concentration of TCA per 100 mL of water, concentration of TCA per 100 mL of solution, concentration of TCA per 100 grams of solutions) the person preparing the solution had better know what he/she is doing!
Salicylic acid can be used up to a concentration of 30% and it is particularly useful for oily skin and comedos, but should not be used in children, teenagers, people allergic to aspirin, or on pregnant or lactating women.
Resorcinol is one of the ingredients of the Jessner solution, which includes also lactic and salicylic acid. A way of getting good activity without having to go too high with the concentrations, hence decreasing the risk of side effects.
Take home message: peels are both useful and dangerous. Please make sure you know what you are doing when before applying one yourself, or choose carefully the esthetician or dermatologist if you decide to have it done professionally.
Update: What SAS offers you
We still don't sell peels as such, but we have some products that may be better for most applications, and are certainly safer. Our alpha/beta exfoliator penetrate deeply into the skin because of its special, non-aqueous carrier, and will help renew your skin without down time.
SAS salicylic wash will help with those pesky comedos and balckheads and will decrease the size of pores. Ideal for people with a tendency to acne.
Chemical peels: the basics.
A peel is a chemical solution that is applied to the skin and allowed to penetrate and wound it in a controlled way. Healing will follow, the old skin will peel and new skin will take its place.
The chemicals used are sometimes called exfoliating or wounding agents. Wounding is a good word for this, because depending on the method, the effect may be second degree burns and the pain so severe as to require general anesthesia.
Who can do a peel?
In chemical peels, a doctor, esthetician, or you, apply a chemical solution to your skin with the objective of destroying it, so that when your skin heals many of the previous visible defects will be gone.
What can go wrong?
The deeper the destruction, the more can go wrong. Some people may heal with scars, in others melanocytes may die leaving spots of hypo-pigmentation; a person with allergy to aspirin may have a bad reaction, etc. For people with “dormant” herpes virus, the peel may induce a re-awakening of the virus and reappearance of symptoms.
What can go right?
Old scars may go away, the same for minor wrinkles, age spots, etc. The deeper the destruction, the more can go right.
What are the options?
Type and concentration of the chemicals used, and how the solution is applied, these variables will determine the depth of the peel.
The chemicals used most frequently in peels are alpha hydroxy acids, trichloroacetic acid, salicylic acid and resorcinol. AHAs are used for superficial peels; TCA is more frequently used for medium peels.
Factors that may affect the depth of a peel include the concentration of the peeling agent, the number of coats that are applied, and the amount of time allowed before the acid is neutralized. Deeper peels result in more dramatic effects as well as higher risks, increased pain, and longer healing time.
Examples of alpha hydroxy acids are glycolic, malic, mandelic and lactic (others are used more for label value than for real value). AHAs differ in pK, which is a measure of the tendency to lose a proton. The higher the concentration of protons, the more acidic the solution will be and the lower the pH, so the lower the pK the stronger the peel will be. Another important factor is concentration: the higher the concentration of the acid, the more protons will be released into the water and the stronger the peel.
Tip: Another label trick used by manufacturers: use a high concentration of acid but add base (like sodium hydroxide) to convert protons into water. You can then have a high concentration of “acid” on the label but most of that acid would have been converted into salt: not much use in a peel but good for sales.
The pK of lactic and glycolic acids is very similar. Why is it then that glycolic peels are stronger than lactic peels at the same concentration? Nothing to do with penetration. The reason is that by using % (weight per volume of solution) we are comparing apples with oranges. This is not an effective way of comparing concentrations. Biochemists use molarity, which compares similar number of molecules. Because the glycolic molecule is smaller than lactic acid, the same weight of chemical will contain more molecules of glycolic acid than of lactic. In a solution this difference will translate into more protons.
TCA and salicylic acids are not alpha hydroxy acids, and they work not simply because of their acidity but through complex interactions with the skin proteins. TCA interacts with water molecules, exposing hydrophobic parts of the protein that would not be affected by the AHAs. TCA is used in concentrations between 25 and 50%, and because % can mean different things (concentration of TCA per 100 mL of water, concentration of TCA per 100 mL of solution, concentration of TCA per 100 grams of solutions) the person preparing the solution had better know what he/she is doing!
Salicylic acid can be used up to a concentration of 30% and it is particularly useful for oily skin and comedos, but should not be used in children, teenagers, people allergic to aspirin, or on pregnant or lactating women.
Resorcinol is one of the ingredients of the Jessner solution, which includes also lactic and salicylic acid. A way of getting good activity without having to go too high with the concentrations, hence decreasing the risk of side effects.
Take home message: peels are both useful and dangerous. Please make sure you know what you are doing when before applying one yourself, or choose carefully the esthetician or dermatologist if you decide to have it done professionally.
Update: What SAS offers you
We still don't sell peels as such, but we have some products that may be better for most applications, and are certainly safer. Our alpha/beta exfoliator penetrate deeply into the skin because of its special, non-aqueous carrier, and will help renew your skin without down time.
SAS salicylic wash will help with those pesky comedos and balckheads and will decrease the size of pores. Ideal for people with a tendency to acne.
Guide created: 07/05/06 (updated 09/26/08)
Thank you for voting. If your vote meets our 
