Salicylic acid, a dangerous active ingredient?

Can salicylic acid irritate the skin?

The salicylic acid is recognised for its exfoliating and purifying action, but it is not without the risk of irritation, particularly during the initial applications. In the first weeks of use, it is common to experience mild discomfort : tightness, redness, stinging or itching. These effects, although unpleasant, are not necessarily alarming. They often indicate the skin’s adaptation to this new active ingredient, which stimulates cell renewal and promotes the elimination of dead cells.

In individuals with sensitive skin, reactions to salicylic acid may be more pronounced.

In this case, it is recommended to decrease the frequency of application (for example, every other evening instead of each night) or to apply the treatment between two layers of moisturiser. Skin tolerance generally improves after a few weeks, but if this does not occur, it indicates that your skin cannot tolerate salicylic acid and you should discontinue its use.

Beyond transient irritations, some allergic reactions may also occur. A recent study conducted between 2020 and 2024 evaluated the sensitising potential of salicylic acid via patch tests performed on 489 patients. Of these, 21 showed a positive response, corresponding to a reaction rate of 4.3%. Interestingly, five patients also exhibited cross-reactivity with other salicylates, suggesting that salicylic acid might serve as an allergy marker for this compound family. However, no severe reactions were observed, and the results indicate that 5% skin tests were generally well tolerated. These observations highlight that, even though salicylic acid can be responsible for allergic contact dermatitis, these cases affect a minority of individuals.

As with any new active ingredient, before using a product containing salicylic acid, we recommend that you test your skin’s tolerance on a small area, such as the crook of the elbow.

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Is salicylic acid incompatible with other active ingredients?

Salicylic acid can be combined with various actives according to the skin’s needs: hyaluronic acid, niacinamide, vitamin C... However, its potent exfoliating action requires some caution when combining it with other molecules that likewise possess an irritating potential. This is not strictly a contraindication, but rather relates to the skin’s ability to tolerate the simultaneous use of multiple exfoliating or sensitising actives.

The combinations to watch are primarily those with AHA-type acids, such as glycolic acid, but also with azelaic acid or even retinoids (tretinoin, retinol, adapalene). These pairings can be beneficial in the long term, notably for skin prone to acne or pigmentary irregularities, but they increase the risk of dryness, redness and flaking if introduced abruptly. For this reason, it is recommended to alternate their use (for example, salicylic acid one evening and retinol another evening).

It is important to listen to your skin: if it begins to exhibit irritation, it is advisable to lengthen the intervals between applications or to bolster hydration.

Should salicylic acid be avoided during pregnancy?

The use of salicylic acid during pregnancy raises many questions. According to the Scientific Committee on Consumer Safety (SCCS), its use is deemed safe when it complies with the maximum concentrations set by the European cosmetic regulation. Furthermore, the Food and Drug Administration (FDA) classifies salicylic acid as a pregnancy Category C drug.

Category	Definition
A	Controlled studies in pregnant women have shown no risk to the foetus during the first trimester (nor any subsequent risk).
B	Animal studies have shown no risk, but no controlled studies have been conducted in pregnant women. Alternatively, animal studies have demonstrated an adverse effect, but this has not been confirmed in humans.
C	Animal studies have demonstrated an adverse effect on the foetus, and no controlled studies have been conducted in women. Use may be justified if the potential benefit outweighs the risk.
D	Positive evidence of risk to the human foetus exists, but use may be considered in serious or life-threatening situations where no alternative medication is available.
X	Animal or human studies have demonstrated foetal abnormalities, or clearly established risks that outweigh any potential benefit. Use is contraindicated during pregnancy.

Categories of medicines according to the FDA pregnancy classification.

In practice, this corresponds to treatments generally containing less than 2% salicylic acid, applied topically to small areas of skin. Under these conditions, the risk of systemic absorption is very low, and experts consider that it poses no particular risk to either the mother or the foetus. However, caution remains advisable: it is recommended to avoid applying over large areas, under occlusion, or on damaged skin, as these circumstances could increase cutaneous penetration and thus entry into the bloodstream.

However, dermatological peels with a high concentration of salicylic acid (≈ 20%) performed in specialist clinics are not recommended during pregnancy.

Regarding breastfeeding, the available data are still limited. Nevertheless, clinical observations suggest that low-concentration topical use does not pose any significant risk, as systemic absorption remains minimal and is unlikely to reach breast milk. As a precaution, however, it is still preferable to restrict application to limited areas and to avoid any contact with the breast.

Is salicylic acid photosensitising?

Currently available scientific data suggest that salicylic acid could act as a photosensitiser under certain experimental conditions. Laboratory studies have shown that this molecule can accelerate the formation of thymidine dimers — a UV-induced DNA lesion — when exposed to light in the 300–350 nm range. This suggests that salicylic acid may amplify certain effects of UV light on molecular structures.

However, these findings remain confined to laboratory settings and do not directly reflect the response of human skin. To date, no clinical study has demonstrated that the topical application of salicylic acid increases photosensitivity or the risk of sunburn. The available research is predominantly concerned with the role of salicylic acid in the protective or regulatory mechanisms of plants exposed to environmental stresses, rather than any deleterious effect in humans.

In practice, dermatologists consider that salicylic acid is not classified among the active ingredients known to cause photosensitisation, but the use of a daily sunscreen remains recommended when using it, due to its keratolytic effect, which slightly thins the skin barrier.

Is salicylic acid an endocrine disruptor?

The salicylic acid has sometimes been suspected of having endocrine-disrupting potential, notably because it belongs to the salicylate family, which also includes acetylsalicylic acid, more commonly known as aspirin. In Europe, it is classified as Category 2 reproductive toxicant (CMR2), that is to say it is suspected of being "toxic to reproduction", without this having been proven. This classification of salicylic acid is based on indirect data rather than solid evidence related to cosmetic use.

In fact, regulations have already extensively assessed its safety. In 2018, the SCCS concluded that salicylic acid is safe at the concentrations permitted by cosmetic regulations. This conclusion was reaffirmed in more recent opinions, the latest being in 2023, which again endorses its safe use. Doubts regarding its endocrine-disrupting potential arise mainly from studies conducted in vitro, that is, under artificial laboratory conditions. However, it is not uncommon for such laboratory findings to fail to translate in vivo, as shown for instance by the case of soya, which contains molecules that mimic oestrogens but do not induce pathologies in humans.

Thus, although it is important to keep abreast of scientific developments in this field, the data available to date do not allow salicylic acid to be regarded as an endocrine disruptor.