7 questions about salicylic acid.

During the initial weeks of use, salicylic acid may cause a temporary flare-up of acne, known as a skin purge, particularly in individuals with skin prone to breakouts, as it aims to clear out obstructions residing deeper within the skin due to its liposoluble nature. This phenomenon occurs due to the ability of salicylic acid to accelerate the rate of skin cell renewal.

When this occurs, the build-up of sebum, dirt, and clusters of dead cells, trapped deep within the pores, are rapidly pushed towards the surface. This then results in the appearance of non-inflammatory microcomedones on the skin surface (whiteheads and blackheads), which may be accompanied by dry skin, irritation, and flaking.

In the absence of treatment, these comedones can lead to inflamed acne spots.

Salicylic acid can be safely used on dark skin. It is even recommended to include this active ingredient in skincare routines. Although acne affects all skin colours, dark skin is more likely to suffer from a post-inflammatory hyperpigmentation and scarring after an acne outbreak. However, salicylic acid can help reduce the risk of acne lesions due to its desmolytic action.

According to the report by the Scientific Committee on Consumer Safety (SCCS), salicylic acid at the low percentages permitted can be used safely during pregnancy or while breastfeeding. However, it has been shown that it can be absorbed to some extent through intact skin, depending on the type of excipient. Although a relatively small proportion is absorbed through the skin and it is unlikely to pose a risk to the child's development, we recommend you to consult a healthcare professional. Indeed, salicylic acid has a chemical structure closely related to that of aspirin. However, the latter is considered risky towards the end of pregnancy, even though further studies are needed. Indeed, a few studies have shown that its use would be associated with miscarriages, congenital malformations, haemorrhagic complications and salicylism.

Glycolic acid, lactic acid... it is known that the topical use of certain actives can increase skin sensitivity to the sun, thus necessitating appropriate sun protection measures. However, this does not appear to be the case with the salicylic acid. Based on studies conducted in humans and mice, the CSSC agrees that salicylic acid does not have photosensitising properties. Therefore, there would be no harm in using it in the morning. On the contrary, salicylic acid may actually have a potential photoprotective effect on the skin. It would exhibit a peak absorption at about 305 - 310 nm in the UVB range.

Two clinical studies have demonstrated that salicylic acid, applied shortly before UV exposure, reduces the risk of sunburn. It has been suggested that the benzene core of salicylic acid absorbs UV energy and converts it into longer wave radiation, which is felt as heat. However, in these experiments, the application of a relatively high concentration of salicylic acid shortly before sun exposure is necessary to achieve "sun protection". Yet, such a concentration (> 2%) can cause over-exfoliation and irritation for regular use.

As a precautionary measure, we recommend applying a sunscreen after using products formulated with salicylic acid. No other additional precautions are necessary.

In 2018, the CSSC issued a positive opinion on the use of thesalicylic acid. It is deemed safe in cosmetic products and is suitable for all skin types.

Advice : Before using salicylic acid, test it on a small area of your skin (inside of your elbow, behind your ear, inner side of your wrist) to check whether or not you are allergic to it. Do not use it if a reaction develops at the site of the patch test.

However, it is possible to experience tingling, a slight sensation of warmth, irritations, peeling, and skin dryness. These side effects can vary depending on the skin type and the concentration used. Salicylic acid is currently regulated under Annex III and Annex V of the Cosmetic Regulation with specific maximum concentrations and conditions of use.

Indeed, rare phenomena of systemic toxicity (nausea, vomiting, dizziness, tinnitus, psychosis, coma, death) have been observed when high concentrations of salicylic acid are applied to large skin areas. Furthermore, its use in oral care products, spray products and hygiene products intended for children under 3 years old is prohibited.

Animal studies have been conducted to assess the carcinogenic potential of salicylic acid. Based on the results obtained, it was deemed to lack such an effect and is non-carcinogenic. Furthermore, according to some research, salicylic acid may exhibit anti-cancer properties.

Concerns have emerged about the potential effects of endocrine disruptors in salicylic acid according to recent studies. European regulations even classify it as a category 2 reproductive toxin (CMR 2). Several studies in vitro and ex vivo have shown a decrease in testosterone production after exposure to acetylsalicylic acid, providing evidence of an anti-androgenic mode of action. Other in vitro and human studies have shown that salicylates can disrupt the thyroid.

However, all studies in vivo, ex vivo and in vitro have been conducted on salicylates, esters (acetylsalicylic acid) or salts of salicylic acid. Therefore, further research is necessary. In response to this controversy, the European Commission asked the CSSC to conduct a safety assessment in cosmetic products. In December 2022, the CSSC issued its opinion and stated that the use of salicylic acid in cosmetic products at the specified concentrations is safe, taking into account the latest data provided.

• SHARPE G. & al. Emollients, salicylic acid, and ultraviolet erythema. Lancet (1990).

• Cosmetic Ingredient Review Expert Panel. Safety assessment of salicylic acid, butyloctyl salicylate, calcium salicylate, C12-15 alkyl salicylate, capryloyl salicylic acid, hexyldodecyl salicylate, isocetyl salicylate, isodecyl salicylate, magnesium salicylate, MEA-salicylate, ethylhexyl salicylate, potassium salicylate, methyl salicylate, myristyl salicylate, sodium salicylate, TEA-salicylate, and tridecyl salicylate. International Journal of Toxicology (2003).

• MAES D. & al. Salicylic acid protects the skin from UV damage. Journal of Cosmetic Science (2006).

• HEARING V. J. & al. The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin. Journal of Dermatological Science (2009).

• STOODLEY M. A. & al. Intracranial haemorrhage in pregnancy. Obstetric Medicine (2009).

• ARIF T. & al. Salicylic acid as a peeling agent: a comprehensive review. Clinical, Cosmetic and Investigational Dermatology (2015).

• Scientific Committee on Consumer Safety (SCCS). Opinion on salicylic acid (2019).