It is a lipophilic beta-hydroxyacid, which cause desquamation of the superficial layers of the skin, with keratolytic and comedolytic effects. It can be also used in combination with other peels to promote better penetration of the second substance. Usually we use hydroalcoholic solutions of salicylic acid at 20–30%. It is very useful for acne, for both inflammatory and noninflammatory lesions, as well as for postinflammatory pigmented lesions. Salicylic acid peel is also indicated to other types of postinflammatory hyperpigmentation, such as melasma and pigmented keratosis. The peeling causes bearable burning sensation. The “end point” for this peeling is the appearance of a homogeneous erythema with a white powder precipitation. It is not necessary to neutralize this peel. Cold compress can be used only to comfort the patient. Coughing and sneezing can occur during the procedure (Salam et al. 2013; Roberts 2004; Grimes 1999).

It is an alpha-hydroxiacid and similar to other compounds in this pharmacologic group, as lactic, citric, mandelic, malic and tartaric acids, glycolic acid peel causes epidermolysis in minutes after application. It promotes skin peeling and scattering of epidermal melanin. The “end point” is reached when a homogeneous erythema, better seen in caucasian patients, or when the first points of frosting (epidermolysis) are noted. For this reason, it is better to neutralize in 2-3 minutes. At this moment, the dermatologist shall neutralize the process. The acid should be neutralized with sodium bicarbonate solution 1% or with saline solution, or even with water. The effects of glycolic acid peel are time dependent. The concentration ranges from 10% to 70% (Roberts 2004).

It is indicated for acne, based on the antiinflammatory property and antibacterial effect against Propionibacterium acnes. Reduction of acne lesions (comedos, papules, and pustules) is observed as well as improvement on the skin pigmentation after glycolic acid peels. Studies have shown that glycolic acid peel at the concentration of 70% is able of to press out pustules and comedos within few minutes (Salam et al. 2013). It is less effective in the treatment of superficial and mixed melasma and postinflammatory hyperchromia. It offers a slightly higher risk of irritation, hypochromia, and hyperpigmentation in a small percentage of patients. With the aim to reduce the irritation caused by this peel, it is better to manipulate the substance in gel vehicle instead of solution and to request for buffering substance with higher pH. The pH of the unbuffered acid ranges from 0.08 to 2.75. A pH less than 2 increases necrosis index and keratinocytes destruction. It increases the rate of complications without increasing its effectiveness. Therefore, we recommend the use of buffered product or at least partially buffered (Roberts 2004).

It causes denaturation of proteins with coagulation necrosis and cell death. The degree of necrosis depends on the concentration and on the number of layers performed. It is not possible to neutralize this acid and denaturation of proteins is observed in seconds. Clinically, the protein denaturation is expressed by the presence of a white color spot called “frosting.” According to the peeling depth, different grades of grayish-white area above the erythema are noted. The frosting is not desirable for dark skin, therefore low concentrations up to 25% of trichloroacetic acid are recommended. It is a very painful procedure with a severe burning sensation (Salam et al. 2013; Roberts 2004).

Al-Waiz and Al-Sharqi (2002) conducted a study about the application of Jessner peeling immediately followed by TCA 35% peeling acne scars treatment in 15 dark-skinned patients. They observed significant improvement (greater than 75% clearance of lesions) in 1 patient, moderate improvement (51–75% of clearance) in 8 patients, mild improvement (26–50% of clearance) in 4 patients, minimal improvement (1–25% of clearance) in 1 patient, and no response in 1 patient. Nine patients (73.4%) suffered from transient postinflammatory hyperpigmentation. In two of them it was preceded by erythema that lasted for more than 1 month. All patients completely recovered 3 months after procedure. Considering the reasonably low efficacy and potential risks involved, we do not recommend this substance for black skin.

Vitamin A stimulates collagen and reduces blemishes. It can be applied in concentration ranging from 1% to 9%. It is used as a cover mask, which should be maintained on the skin from 4 to 8 h. After this period it should removed with a cleanser (Salam et al. 2013). The scales start to flake after 3–4 days and last more 2–3 days. It is effective for acne, for pigmentary disorders, and for rejuvenation. It is very safe for darker skin phototypes. It usually does not cause any discomfort during the procedure. It has a canary yellow color, but is commonly formulated with a tinted vehicle, simulating a cosmetic foundation, allowing the patient to go out of the office just after the procedure (Fig. 1).

Jessner solution contains lactic acid, salicylic acid, and resorcinol. It is excellent to be used as a superficial peel or to be combined with other peel. Its great advantage is the synergistic action of the three keratolytic components. It has a good lightening action due to resorcinol, a phenolic compound (Roberts 2004). However, it is important to emphasize the care and attention when using this peel on skin types V and VI, as resorcinol can cause depigmentation in these patients. The target is to achieve a homogenous erythema with a whitish precipitation (similar to salicylic acid peels) without frosting. It is not necessary to wash or neutralize. This peel also promotes burning sensation and if an exaggerated reaction is realized, the procedure should be interrupted (Fig. 2).

In some cases we can do a focused peeling. It consists of applying the chemical peel on a localized small area, maintaining the surrounding skin undamaged. It is very useful for localized injuries, such as hyperpigmentation, solar lentigines, seborrheic keratoses, active acne, or acne scars (Burns et al. 1997). The most common peels used with this purpose are salicylic acid (20–30%), Jessner solution, and TCA (20–30%). It is possible to combine two different substances on the area to be treated through spot peel method associating with another substance for the entire face. It also describes the use of different concentrations of the same substance, higher concentration as spot peel and low concentration on the entire face (Salam et al. 2013; Roberts 2004; Al-Waiz and Al-Sharqi 2002).

Chun et al. (2004) reported excellent results with spot peel using TCA (10–65%) for pigmentary lesions (solar lentigines, melasma, and freckles) in oriental individuals with skin phototypes IV–VI. Seborrheic keratoses and lentigines presented the best results, and melasma showed higher relapse rate. The substance was applied with fine-tipped wooden sticks (toothpicks) inside the lesion with pressure. Surprisingly, no severe side effect was reported with higher concentrations.