What are the potential risks associated with using an eyelash and eyebrow serum?

The eyelash and eyebrow serums are applied to very sensitive areas in immediate proximity to the eye. When a cosmetic product is deposited at the lash root, it can gradually migrate to the ocular surface under the combined action of blinking, perspiration, and skin warmth. This "migration" phenomenon typically occurs within minutes and explains why some treatments can cause burning sensations, stinging, redness, or ocular discomfort. In some cases, repeated exposure may promote the onset of conjunctivitis, blepharitis, or, less commonly, eye infections.

From a regulatory perspective, European legislation mandates that any cosmetic product intended for the eye contour or eyes undergo specific tolerance tests before it is marketed. These evaluations aim to minimize the risks of irritation and ocular toxicity.

That being said, according to individual sensitivity, adverse effects may still occur. The cutaneous and ocular reactions related to eye makeup products are well documented in the literature. In fact, one study evaluated the irritant potential of several mascaras using occlusion tests on healthy volunteers. Two of the seven mascaras induced skin inflammation with redness, necessitating premature termination of the tests. These products were distinguished by their formulation based on solvents derived from petroleum distillates, as opposed to the other mascaras formulated as conventional emulsions. Some also contained surfactants strongly irritating, known to disrupt the skin barrier, such as sodium lauryl sulfate.

Beyond acute irritation, prolonged and repeated use of products applied to the eyelashes can also be associated with more insidious ocular damage. Several clinical reports have documented complications linked to chronic mascara use, including conjunctival lesions, eyelid dermatitis, infectious keratitis, and tear duct obstructions. In one case series, two patients presented with non-melanocytic conjunctival pigment deposits after years of intensive mascara application, while another patient developed a tear duct obstruction caused by a conglomerate of makeup residues. These observations suggest that pigments and particles from eye products can gradually accumulate on the ocular surface or within the tear drainage pathways.

This study underscores that cosmetics applied to the eyelashes and eyebrows are not innocuous in the long term, particularly when used daily or without rigorous makeup removal.

The risks associated with eyelash and eyebrow serums depend above all on the ingredients they contain. Some active ingredients, although highly effective at stimulating the hair growth, can cause significant adverse effects, especially when used over prolonged periods near the eye.

Prostaglandin and its derivatives: ingredients to avoid.

Prostaglandin analogs are arguably the most controversial active ingredients in eyelash and eyebrow serums. Originally, prostaglandins are hormones involved in numerous physiological processes. Some of their derivatives are also used in ophthalmology, particularly in eye drops for glaucoma treatment, where they help reduce intraocular pressure. One of their well-documented side effects is a marked stimulation of eyelash growth, observed in treated patients.

It was on the basis of this clinical observation that these molecules were repurposed for cosmetic use to promote the lengthening and thickening of eyelashes and eyebrows. While their efficacy is undeniable, their tolerance profile is problematic. Numerous adverse effects have been reported: eyelid redness and edema, burning or tingling sensations, tearing, skin hyperpigmentation along the lash line, long-lasting iris darkening, decreased intraocular pressure, and even unwanted hair growth in the areas where the product contacted the skin.

From a regulatory standpoint, these substances are subject to heightened monitoring. In the United States, their use in eye cosmetic products is strictly regulated by the FDA. In Europe, the German Federal Institute for Risk Assessment determined as early as 2018 that prostaglandin derivatives used to stimulate eyelash growth could pose a health risk, even at the concentrations employed in cosmetics. Following a call for data issued in 2020, the Scientific Committee on Consumer Safety (SCCS) concluded in 2022 that the use of these analogues in cosmetic products is not without risks to consumers.

Good to know : In INCI lists, prostaglandin analogs can often be identified by the presence of the segment "prost", for example: Isopropyl Cloprostenate, Ethyl Tafluprostamide, Dehydrolatanoprost, Bimatoprost or Cyclopropyl Bimatoprost.

Phenoxyethanol, a suspected ocular irritant that warrants caution.

Phenoxyethanol is a preservative synthetic compound used in cosmetics to limit microbial proliferation. Although permitted under European regulations within specific concentration limits, it is regularly flagged for its potential to irritate the eyes.

Several health authorities, including the French National Agency for the Safety of Medicines and Health Products (ANSM), acknowledge that the phenoxyethanol can cause moderate to severe ocular irritation. Cases of stinging, redness, and tearing have been reported, raising concerns when used in products applied directly adjacent to the eye. In an eyelash or eyebrow serum, where the risk of migration onto the ocular surface is real, its presence may therefore be questionable.

Note : The list of ingredients mentioned above is not exhaustive. Other components may be problematic in eyelash and eyebrow serums. Among them are certain irritating or sensitizing preservatives, such as formaldehyde releasers (DMDM Hydantoin, Imidazolidinyl Urea...) or the Benzalkonium Chloride, known for its potential to irritate the ocular surface. Fragrances and fragrance allergens, such as limonene, linalool, or geraniol, even at low concentrations, can also trigger reactions in sensitive individuals. Finally, certain denatured alcohols may cause stinging sensations around the eyes.

• WESSMAN C. & al. Mascaras may cause irritant contact dermatitis. International Journal of Cosmetic Science (2002).

• MEYER D. & al. Ocular manifestations of long-term mascara use. Ophthalmic Plastic & Reconstructive Surgery (2009).

• Comité scientifique spécialisé temporaire. Utilisation du phénoxyéthanol dans les produits cosmétique. ANSM (2017).

• Scientific Committee on Consumer Safety (SCCS). Opinion on prostaglandins and prostaglandin-analogues used in cosmetic products (2022).

• DIMRI A. G. Microbial contamination of eye make up product: Herbal mascara a concern. Universities Journal of Phytochemistry and Ayurvedic Heights (2022).

• KUNDER R. & al. Microbiological contamination linked to the usage of mascara among waterproof and non-waterproof brands and tear film assessment. AJ Journal of Medical Sciences (2024).