Chemical peels – The Complete Guide

Table of Contents

What is a chemical peel?

A chemical peel is the application of one or more agents (it’s usually an acid solution). It helps to strip away the skin’s top layers in a controlled manner. This removes a portion or all of the epidermis (it is outermost layer of the skin) and the dermis (deeper most layer of the skin). This stimulates the skin to renew and regenerate. It helps to improve and smooth the texture of the skin.

Depending on the strength of these formulations. these procedures can be done in-office by a specialized dermatologist or plastic surgeon, registered nurse or a aesthetician, or by yourself at home.

What are chemical peels used for?

Skin laxity
Lentigines or liver spots
Ephelides (freckles)
Pigmentation (melasma. post-inflammatory hyperpigmentation)
Acne
Rosacea
Scarring (acne scars- hypertrophic and atrophic scars, surgical scarring, traumatic scarring)
Pre-cancerous growths (actinic keratoses)
Skin texture (uneven, dull skin tone)
Sun damage (it can be sun spots,fine lines and wrinkles)

Chemical peels wont do much for treating deeper wrinkles and scars, or severe sun damage.

Who should avoid chemical peels?

Active infections
Allergy to chemical peels
Isotretinoin therapy within the previous 6 months for medium-depth and deep chemical peels.
People with open wounds
Chemical peels are not safe for pregnancy
People who has inflammatory skin conditions such as rosacea, eczema, and psoriasis should use chemical peels with caution
Radiation exposure
People who had recent facial rejuvenation therapy should use peels with caution
Darken skin types or skin of colour should use peels with caution.

Commonly used acids in chemical peels:

AHA’s (alpha-hydroxy acids)

AHAs such as glycolic acid, lactic acid, and mandelic acid is great for general exfoliation, acne, fine lines, wrinkles, and hyperpigmentation (melasma, PIH). It also has moisturizing properties. Mandelic acid is more suitable for sensitive skin and skin of colour than glycolic acid and lactic acid (can cause irritation).

BHA’s (beta-hydroxy acids)

Salicylic acid is also used for general exfoliation, acne, fine lines, wrinkles, and hyperpigmentation (melasma, PIH), but it doesn’t have moisturizing properties. Salicylic acid can cause irritation in sensitive skin and skin of colour.

PHA’s (poly-hydroxy acids)

PHA’s such as gluconolactone, lactobionic acid, and galactose is great for general exfoliation, fine lines, wrinkles, and hyperpigmentation (melasma, PIH). It also has moisturizing properties, but not so good for acne. PHA’s are safe to use for sensitive skin and skin of colour.

Other commonly used acids in chemical peels:

Azelaic acid (safe).
Niacinamide (safe).
Retinol (use with caution).
Vitamin C (use with caution).

Different acids at lower concentrations can also be mixed (blended peels). The results a peel can have on the skin depend on:

Type/properties of the acid used (mentioned above)
Product/acid formulations
The patient’s skin type (or any other existing skin condition), and
Peeling technique.

Factors that influence the peel strength:

1. Type/properties of the acid:

a. Molecular size: the smaller the molecule, the higher the potential to penetrate deeper (for example, glycolic acid). If the molecule is large, then it won’t go deep into the skin (for example, mandelic acid).

b. pKa (strength of the acid): acids can be free (more present at lower pH) or dissociated (more present at higher pH) in solution. Free acid is what penetrates through the skin and is the relevant form in chemical peels. pKa is the pH at which half of the solution is in a free acid form.

pKa values of some hydroxy acids:

Glycolic acid: 3.53
Mandelic acid: 3.41
Lactic acid: 3.86
Salicylic acid: 2.97

2. Product/acid formulations:

a. Concentration of the acid: the higher the concentration of the acid, the stronger the peel, if the concentration is low, then the peel will be less strong. A low percentage in one acid can actually be a great deal stronger than a higher percentage in another acid because of the molecular acid, pKa of the acid, and pH of the formulation.

b. Product pH: It means how acidic or basic an aqueous solution is. This determines how much free acid is in a peeling solution. When the pH of a solution is equal to the pKa of the acid, this means that only 50%of the acid is in its acid-free form. The lower the pH of the product, the more free acid there is to penetrate into the skin.

3. Patient characteristics:

Skin preparation (skin care prior to procedure, previous procedure)
Skin type (thick sebaceous or thin dry skin)
Area of the body treated (face, neck, or back)
Checking the health of the skin barrier.

4. Application technique:

The amount of time the peel is in contact with the skin.
Application pressure.
Number of layers of the peel.

Types of Chemical peels:

Superficial peels
Medium-depth peels
Deep peels

Superficial peels:

Superficial peels can penetrate to the epidermis only. It can also go deeper to reach the basal layer. Very superficial peels can remove the stratum corneum.

What are superficial peels used for?

Superficial peels can treat acne, dullness, superficial scars, fine lines, hyperpigmentation, and uneven texture. It is safe to use for Fitzpatrick types 1-6. It is best done by a board-certified physician (dermatologist or plastic surgeon), registered nurse, licensed aesthetician, or can be done at home.

Follow up for superficial peels:

It can take 1-7 days to heal (might have mild flaking without much downtime). Superficial peels can be done every 2-5 weeks, and it may take 3-5 treatments for results.

Examples of Superficial peels:

Very superficial peels: glycolic acid (10-50%), lactic acid (50%), salicylic acid (20-30%), TCA<10%.
Superficial peels: glycolic acid 50-70%, TCA 10-30%, Jessner’s peel (lactic acid + salicylic acid + resorcinal, these peels are milder than TCA).

Side effects of Superficial peels:

Post-inflammatory pigmentary alterations (PIH), erythema, Itchy skin , burning, redness, scabbing, swelling, and superficial desquamation/epidermolysis (shedding of skin).

Medium-depth chemical peels:

These peels can remove the entire epidermis and papillary (upper) dermis.

What are Medium-depth peels used for?

Medium-depth peels can treat deep scars, skin laxity, fine lines, wrinkles, uneven skin tone (pigmentation), pre-cancerous growth, sun damage (sun spots).

Use with caution for Fitzpatrick types 4-6 (can cause scarring or pigmentation). It is best performed by a board-certified physician.

Follow up for medium-depth peels:

Medium-depth peels can take 7-14 days to heal (you might see significant crusting and peeling after a few days)

Examples of Superficial peels:

Glycolic acid: medium to high concentration, with or without pre-treatment primer such as Jessner’s solution.
TCA: low to medium concentration, with or without pre-treatment primer such as Jessner’s solution.

Side effects of Superficial peels:

Post-inflammatory pigmentary alterations (can cause pigmentation), superficial bacterial or fungal infection, reactivation of HSV (virus), scarring (scars on skin), milia, acneiform eruption (acne in form of papules and pustules), greater thickness desquamation/epidermolysis (shedding of skin).

Deep chemical peels:

Deep chemical peels help to remove the entire epidermis, papillary dermis, and may extend to the reticular (mid) dermis.

What are deep chemical peels used for?

It can treat deep scars, deep wrinkles, sun damage, uneven skin tone (pigmentation), skin laxity, and pre-cancerous growths. Safe to use for Fitzpatrick 1-3. It is best performed by a highly specialized physician.

Follow up for deep peels:

It can take about a month or more of downtime. It is usually a single procedure.

Examples of deep peels:

TCA > 50% (monolayer application, with pre-treatment primer such as Jessner’s solution) and Baker’s phenol peel.

Side effects of deep peels:

Post-inflammatory hyperpigmentation, secondary bacterial or fungal infection, reactivation of HSV (virus), scarring (scars), milia, acneiform eruption (acne in form of papules and pustules), cardiotoxicity/arrhythmia (damage to the heart muscle, due to systemic absorption of phenol, seen in 34–50% of patients), hepatotoxicity (liver damage), nephrotoxicity (kidney damage).

Application of Chemical peel:

The number of application layers should be done based on the desired depth of keratocoagulation ( it coagulates the skin’s proteins together, once the skin proteins are together, they will show as a slight frosting. This frosting means that the chemical peel has done the job and now it has to be neutralized. ).

The multi-layer application will increase penetration, taking the acid further into the dermis, creating a deeper peel (should be careful).

Uniform application of peeling agents should be applied to all areas until desired frosting is achieved

Level 1 frosting is erythema with stringy or blotchy frosting.
Level 2 frosting is white frosting with erythema showing through.
Level 3 frosting is the penetration through the papillary dermis. It has a solid white enamel frosting with little or no background of erythema.

Termination of the chemical peel:

After a desired level of keratocoagulation is reached, the dermatologist will initiate neutralization of the chemical peel by using dilute sodium bicarbonate solution or by using cold saline compresses. This can prevent further ablation (removal of the skin.

Agents that need neutralization are: mandelic acid, glycolic acid, lactic acid, pyruvic acid, and TCA ( Trichloroacetic acid) peels.

Post-procedure:

You can apply cold compresses to the treated exfoliated areas, followed by a moisturizer and a physical blocker sunscreen.
For the first 24 hours, start gentle cleansing with a dilute acetic acid solution (1:100 dilution) four times a day for antibacterial and antifungal treatment, after that make sure to moisturize.
After the first 24 hours, you can start your normal routine with a gentle non-detergent cleanser, followed by a moisturizer.
Make sure to stay indoors and avoid the sun for some time (ask your doctor) and always use a physical sunscreen blocker when heading out. You can also carry an umbrella or wear a broad-brimmed hat.

Other details:

The same type of acid can penetrate differently by virtue of its concentration.
If deeper penetration is involved, then there is a possibility of side effects.
Lower concentrations are also available as non-peeling agents like cleansers, toners, spot treatments, lotions (like 2% salicylic acid).
The selection of the acid, concentration, and level of penetration depends on your skin type, goals, and budget.

How is at-home or DIY chemical peels different from the one done IN-office by the dermatologist?

Both typically use the same kinds of acids. At-home peels will either contain just one acid or a mixture of several, and are in the form of peeling solutions, masks, and pre-soaked chemical peel pads. Depending on the product, these at-home peels will either need washing off after a certain amount of time, or will be left on the skin.

In-office peels have the following properties compared to at-home ones:

Higher concentrations: for example: for glycolic acid many over-the-counter products max out at 20%, while professional peels can reach as high as 70%.

Lower pH: this increases the amount of free acid that can penetrate the skin, which also comes with a higher risk of side effects.

Less guesswork in finding the right acid and concentration: for your skin type and skin concerns, and the right treatment. The professional will know how long the acid should be left on. They will also monitor your skin for any reactions – swelling, erythema, frosting, and any other signs, or else the chemical peel could progress too deeply.

In-office peels are generally stronger, so you expect better results.

Extra details on In-Office peels:

The results of in-office chemical peels will depend on the person performing the peel, and the proper selection of patients and peeling agents. They will look at your skin colour (darker skin colours should be treated with caution) before performing the procedure.
Some patients may need a pre-peel skin care plan for a few weeks. This can improve results and reduce side effects.
Some side effects can be expected, but they can be solved by experts in chemical peels.
During the consultation, you can tell your skin goals, skin type, and budget.
Don’t be afraid to ask questions, and also the side effects that can occur during the procedure.
Follow post-peel skin care instructions to the letter. If none are provided, ask for them.

Tips on At-Home Peels:

Try to find the best acid for your skin type and concerns. You can always consult a doctor.
Try to conduct a patch test before using the product.
Start with low concentrations 5-10% is enough. It’s best to do very superficial peels at home.
Start once a week. Increase it to 2x a week if tolerated.
You can start with peels meant to be washed off rather than left on, especially for sensitive skin and skin of colour.
Use gentle skincare a day or two after peeling. It’s better to skip irritating actives (like retinol and vitamin C), if your skin is peeling or if you have irritation.
If you have over-exfoliated, stop using the chemical peel. Allow the skin to heal with gentle skincare products. You can restart the actives when your skin has recovered (2-4 weeks).
Look for more hydrating chemical peels like hyaluronic acid, green tea, aloe vera, squalene, etc.
Remember to use a moisturizer after a peeling product. Also don’t skip your sunscreen.
Set expectations – at-home peels are not as effective as at-office peels.

Frequently asked question:

Can chemical peels thin out the skin?

No, chemical peels do not thin the skin. They actually thicken the skin by stimulating collagen production and promoting cell turnover.