What is Salicylic acid

Salicylic acids (SA) are naturally found in the bark and leaves of the willow, but can also be made artificially [1], [2], [3], [4]. The use of SA dates all the way back to the old Egyptians, Hippocrates, and Galen to ease pain and reduce fevers. Furthermore, it was also used topically to treat skin disorders, calluses, and corns[2].

SA is a starting material for acetylsalicylic acid (the active drug in Asprin), and an ingredient in many skin care products due to its keratolytic, fungicidal, bacteriostatic, and photoprotective properties. [2], [3]. SA was first described as a -hydroxy acid, however, this is incorrect since both carboxyl groups are directly attached to the aromatic ring and display acidic properties unlike true beta hydroxy acids [2], [5].

Examples of where to find SA in products could be topical formulations for acne, or acne patches. Anti-dandruff shampoos, where it help loosen the “glue” between the cells which in turn promotes the clearing of dead skin cells from your scalp [6]. Due to its comedolytic properties, it helps the penetration of other topical agents such as vitamin A [4]. In Addition, it functions as a mild antiseptic, by preventing the growth of bacteria by downregulating essential factors for bacterial replication. Treatment of wart infections, by dehydrating the cells which in turn leads to the shedding of affected cells by the wart. Moreover, it aids in the activation of your immune system to target the viral wart infection[5], [7].

Scientific Committee on Consumer Safety (SCCS)
Safety in relation to potential endocrine disruption

– Safe to use as a preservative in cosmetics at a concentation of 0,5% . ( with current restrictions in place and information that shows it as an eye irritant that can cause damage to the eye. )
– Not applicable to any spray products,

For other purposes than preservative in cosmetics SCCS considers SA safe to use;

– 3,0% for rinse off hair products
– 0,5% for  body lotion, eye shadow, mascara, eyeliner, lipstic, non-spray deodorant
– 2,0% for all other products [7]

What is the problem and what do the experts say

DTU National Food Institute published their report in 2018 concluding salicylic acid met the criteria for being a hormone disrupting substance. They found moderate evidence for reduced testosterone levels and sperm production.

When having a closer look at the report from DTU, the majority of the studies they refer to investigate derivates of SA, such as acetylsalicylic acid, Sodium salicylate, only a few refer to SA itself. Consequently, any conclusions drawn require careful consideration. For instance, SA is a major metabolite of Aspirin, however, other metabolites of Aspirin may have affected the results. Although it was clear from this report, that it lacks information about SA, we at Allergy Certified prefer to take extra precautions to ensure the safety of consumers, therefore we banned the use of salicylic acid until further research was made [8].

Allergy Certified opinion

In light of the study from DTU, SCCS was requested to conduct a new safety assessment, published in 2023. During this process, they meticulously reviewed DTU report alongside other available data. As a result, it was not possible for SCCS to associate observations made on Aspirin to SA. With the available data SCCS conclude that there are no adverse effects through endocrine mechanisms and that SA is safe to use with the current regulations. [7].

It is important to consider the context- specifically the different routes of administration, dosages, and purpose of the substances. Aspirin is a drug taken orally while SA in cosmetics is applied topically, primarily acting on the skin. Consequently, the potential risk may differ significantly. According to CIR´s exposure assessment, the estimated exposure of daily use of cosmetics containing SA would correspond be only 20% of the level seen when ingesting a baby aspirin. CIR´s concluded that SA is safe in cosmetics with the present regulations [4].

Additionally, according to the US, EPA´s Endocrine disruptor Screening Program, found no significant endocrine disrupting activity with SA. SA displayed no activity in various estrogen or Thyroid receptor assays. Out of 15 androgen receptor assays only one out of 15 androgen receptors registered marginally above cut-off value and was deemed inconclusive. Thus, there was no indication that SA affected the endocrine activity in these systems[7], [9].

Based on the available data, we are confident that SA does not pose any risk to the endocrine system. SCCS, CIR, EPA all find it safe to use with the established guidelines. Therefore, we see no reason for concern regarding use of SA in cosmetics.

Literature:

[1] Norn et al., Dan Medicinhist Årbog, 2009

[2] Arif, Clinical, Cosmetic and Investigational Dermatology, 2015

[3] Mamaligka & Dodou, Gels, 2024

[4] CIR Safety Report, 2019

[5] Kornhauser, Clin Cosmet Investig Dermatol, 2010

[6] Ranganathan & Mukhopadhyay, 2010

[7] SCCS Opinion, 2023

[8] DTU Report, 2018

[9] US EPA Endocrine Disruptor Program