Nail varnish: what are the risks?

Is painting your nails a risky practice?

Whether it's for a special occasion or a simple daily indulgence, painting one's nails is a habit deeply ingrained in many people's routines. However, behind this seemingly harmless act, there are several questions about the potential health risks it poses. Indeed, between the inhalation of potentially toxic vapours, the skin absorption of chemical substances, and the effects on the nail structure, several issues deserve to be addressed. The first problem posed by nail varnishes is their high allergenic potential. Indeed, it is not uncommon for nail varnishes to cause redness and itching around the nails, or even on other parts of the body following accidental transfer, particularly in people with atopic skin. These allergies are particularly common with semi-permanent varnishes.

Furthermore, while the application of nail varnish enhances the appearance of nails, it can paradoxically weaken them over time. Several factors contribute to this effect, including chronic exposure to resins and plasticisers found in varnishes, which can alter the structure of the nail's keratin. Solvents, essential in a nail varnish formula for ensuring quick drying, can also alter the nail's natural lipids as they evaporate, making it drier and more brittle. This is one of the reasons why it is advised not to have consecutive manicures and to take breaks in between.

However, the real danger posed by nail varnishes is the inhalation of their fumes. As soon as a bottle is opened, a strong smell escapes, indicating the presence of volatile organic compounds. These are the solvents in nail varnishes. While they allow the varnish to dry quickly by evaporating into the air, they are inadvertently inhaled. Occasional exposure is not necessarily dangerous, but repeated and prolonged inhalation can be problematic. Indeed, in poorly ventilated environments, the volatile solvents of nail varnishes can cause respiratory tract irritations, headaches, and dizziness, especially with frequent use. These effects are even more pronounced for beauty professionals, who are exposed daily to the emanations of varnishes and removers, increasing the risk of chronic respiratory disorders.

A study assessed the exposure of nail salon workers to volatile organic compounds using five types of nail varnish among the most popular in the United States. The simulated scenario involved applying varnish to 32 nails every 15 minutes during an 8-hour workday, in a test chamber with controlled airflow. The results revealed that the concentrations of butyl acetate (161-330 ppm) and ethyl acetate (440 ppm) exceeded safety thresholds (respectively 150 ppm and 400 ppm). Additionally, formaldehyde was present at concentrations ranging from 0.12 to 0.22 ppm, above the limit of 0.10 ppm. This highlights the high exposure risks to these potentially dangerous volatile solvents in nail salons and demonstrates the need to increase ventilation and raise workers' awareness of the hazards associated with these products.

The occasional use of nail varnish in a domestic setting is not inherently dangerous, but prolonged exposure in a professional context raises more concerns.

A closer look at problematic ingredients contained in nail varnish.

The concerns raised by nail varnishes stem from the ingredients used to formulate them. Here is an overview of the most common molecules in nail varnishes and their potential risks.

Acetone : Acetone is one of the most commonly used solvents in nail varnishes, as it allows for the rapid dissolution of the formula and promotes quick drying. However, acetone is highly volatile and irritating to the skin, eyes, and respiratory tract. Prolonged exposure to this solvent can dry out the nail, cause skin irritations, and neurotoxic effects, such as headaches, dizziness, and nausea.
Toluene : Toluene is another solvent frequently used in nail varnishes. However, it poses health risks. It is considered toxic to the central nervous system and can lead to symptoms such as dizziness, nausea, and headaches when inhaled. Additionally, it is suspected to be carcinogenic and to have harmful effects on foetal development and fertility.
Formaldehyde : Formaldehyde is frequently used in nail varnishes to strengthen the nail structure. However, this compound is classified as a "possible human carcinogen" in Europe and is considered a potential endocrine disruptor.
Butyl Acetate : Butyl Acetate is a solvent often added to varnishes to provide a fluid texture. Although it is less hazardous than acetone, it is still irritating to the skin and respiratory tract and can also cause headaches, dizziness, and nausea when inhaled in high doses.
Dibutyl Phthalate (DBP) : This is a plasticiser used to make nail varnishes more supple and flexible. However, this compound is an endocrine disruptor, exposure to which is linked to fertility issues. Although more and more brands have removed it from their formulas, it is still present in some products.
Parabens : The parabens are preservatives that can potentially cause irritation and allergies, and are suspected to be endocrine disruptors. They can be found in many personal care products, including nail varnish.
Camphor : Camphor is an ingredient used in certain varnishes to give them a flexible texture. Although it is relatively safe at low doses, prolonged exposure to camphor can cause respiratory tract irritation, headaches, and dizziness. At high doses, camphor is also considered toxic to the nervous system.
Xylene : Xylene is a solvent that provides a smooth and fluid consistency in nail varnishes. However, it is also an irritant to the skin and respiratory tract. In the event of prolonged exposure, xylene can cause damage to the liver, kidneys, and central nervous system.
Styrene : Styrene is used in some varnishes to enhance their adherence to the nail. However, since 2019, the International Agency for Research on Cancer (IARC) has classified it in Group 2A as a probable carcinogenic agent for humans.
Rosin : Rosin is a natural resin sometimes added to varnishes to enhance their adhesion. However, its inhalation is associated with the occurrence of respiratory problems.

Do risk-free nail varnishes exist?

In response to growing concerns about the ingredients found in nail varnishes, an increasing number of brands are turning to alternatives that aim to be safer and more health-conscious. This is particularly the case for those offering "free-from" formulations (3-free, 5-free, 7-free, etc). "3-free" nail varnishes do not contain toluene, formaldehyde, or dibutyl phthalate. "5-free" products go a step further by also excluding acetone and camphor, while "7-free" and "10-free" formulations eliminate even more ingredients, such as butyl acetate, styrene, or parabens. These varnishes are often considered interesting alternatives for pregnant women.

Despite the benefits of these varnishes, it's crucial to emphasise that no nail varnish is entirely risk-free. Indeed, terms such as "3-free", "5-free" or "7-free" do not adhere to a universally established standard, making it challenging to guarantee the safety of these products. This was particularly highlighted in a 2018 study that examined the composition of 40 "free" varnishes from 12 different brands. The figure below illustrates the lack of uniformity among the various "free" nail varnishes.