There are several high-concentration chemical peels used in acne scar treatment at dermatologist and cosmetic surgery clinics. Trichloroacetic acid (TCA) peels are a popular option for aggressive chemical peels. When used in high concentration, TCA removes the outer layer of the skin, the epidermis, which can improve the appearance and evenness of the skin.
Aggressive peels may also cause some mild damage to the underlying tissue, which can stimulate a healing response that can improve the structure of the matrix underneath the skin. Aggressive chemical peels are an invasive procedure. They can be quite painful and usually require local anesthesia. The recovery period can be several weeks or even months, and the initial side effects can be severe. There is a relatively high risk of permanent damage to the skin when undergoing this type of therapy and it is critical that these procedures are performed in a professional, clinical environment.
Trichloroacetic Acid (TCA) Facial Peels
Trichloroacetic Acid (TCA) is one of the most common types of chemical used in facial peels. Depending on the concentration, TCA can produce a very superficial or a very deep peel. TCA is a small molecule that is structurally similar to acetic acid (vinegar).
When TCA is applied to the skin, it disrupts and precipitates the proteins in the skin, leading to cell death in the treated tissue. After a short period, the treated tissue sloughs off, allowing space for the regrowth of new, healthier tissue. Low concentration TCA peels (5-15% TCA) produce a very superficial peel, generally with only the outermost layers of the epidermis affected. Some of these low concentration TCA peels are available over the counter.
Medium concentration peels (15-40% TCA) produce a deeper peel, and are generally only available in dermatology and cosmetic surgery clinics. Medium strength peels are fairly common, and offer a balance between effectiveness and side effects. All chemical peels of moderate to high strength have side effects like inflammation, redness and pain that last for at least a few days (up to weeks for strong peels).
High strength TCA peels (40-90% TCA) can be very invasive with a long recovery period. There is also a relatively high risk of scarring and other damage with high strength TCA peels. High strength TCA solutions are sometimes used specifically on acne scars to disrupt the scar tissue that lines and underlies the scar. This process is called CROSS (chemical reconstruction of skin scars) and involves using an applicator to apply high concentration TCA directly into the depression of the scar. This technique minimizes the risks and recovery times associated with full facial peels.
Phenol (aka carbolic acid) was once a fairly common option for medium to deep chemical peel applications, but has been gradually losing popularity. Phenol is a small molecule that is commonly used in the manufacture of plastics and in scientific research laboratories to separate protein from DNA.
In low concentrations, phenol has an analgesic effect and has been used in oral analgesic sprays (e.g. Chloroseptic) and in sunburn relief lotions. At higher concentrations, phenol denatures proteins and causes cell death, much like TCA. Ingestion of significant amounts of phenol is toxic. Phenol disrupts normal heart function and patients undergoing phenol chemical peels must be monitored and intra-venously hydrated during treatment. Because of this and the elevated risk of skin damage when compared to TCA peels, phenol chemical peels are becoming less common.
Croton Oil Peels
Croton oil is a naturally occuring oil that is produced from the seeds of Croton tree. The oil has been used for centuries in traditional medicine, and has also gained a following in modern western medicine. Croton oil causes irritation and cell death in the skin, when applied topically. When ingested it produces diarrhea, and at high exposure levels, death. Croton oil has a similar exfoliating effect on the skin as phenol, and can be combined with phenol as an adjuvant.
References and Sources
Acne scarring: A review and current treatment modalities.
Rivera, 2008. For article abstract, click here.
Focal Treatment of Acne Scars With Trichloroacetic Acid: Chemical Reconstruction of Skin Scars Method.
Lee, et al. 2002. For article abstract, click here.
Histologic Study of Depressed Acne Scars Treated with Serial High-Concentration (95%) Trichloroacetic Acid.
Yug, et al. 2006. For article abstract, click here.
The 2-Day Light Phenol Chemabrasion for Deep Wrinkles and Acne Scars: A Presentation of Face and Neck Peel.
Rullan, et al. 2004. For article abstract, click here.