A closer look at semi-permanent nail varnish.

Semi-permanent varnish is a long-lasting varnish with enhanced shine that can last up to three weeks. This type of varnish helps to avoid the frustration of seeing the colour of your nails chip just a few days after your manicure. Unlike the very liquid texture of a standard nail varnish, the texture of a semi-permanent varnish is closer to that of a gel. Once applied and hardened on the nails, it is resistant to rubbing or chipping during dishwashing or household chores. Resistant to all shocks, semi-permanent varnish ensures coloured and shiny nails for an extended period.

When examining its formulation, the semi-permanent nail varnish is composed of photosensitive acrylic resins. Unlike traditional varnishes that dry in open air, semi-permanent varnish only hardens under the action of a UV or LED lamp, through a process of photopolymerisation. This chemical reaction transforms the oligomers present in the formula into a rigid polymer network, thus creating an adherent, smooth, and solid layer on the nail. The curing time varies depending on the technology used: approximately 2 minutes under a UV lamp, and 30 to 60 seconds under an LED lamp.

The application of a semi-permanent nail varnish is almost like that of a traditional varnish and requires method and precision. It can be done at home or in a salon. Before any application, it is essential to properly prepare your nails. This involves careful cleaning, followed by filing to even out the edges and a light buffing of the nail surface, to eliminate irregularities and improve the adherence of the varnish. The cuticles should then be pushed back with a wooden stick and the nails thoroughly degreased using a cotton pad soaked in nail varnish remover. This ensures a good hold of the nail varnish.

Once the nails are prepared, it is appropriate to apply a clear varnish, known as a base coat, which acts as a protective film between the nail and the pigments contained in the semi-permanent varnish. Once the base is dry, you can proceed with the semi-permanent varnish, using the three-stroke method: one stroke in the middle of the nail, one on the left and then another on the right. Ensure to not apply too much material, to limit the risk of overflow. The varnish must then be hardened under a UV or LED lamp for a few minutes. Generally, to achieve a uniform finish, it is recommended to apply two coats of nail varnish. Finally, you can apply a clear finishing varnish, known as a top coat, to seal the whole and provide additional shine and protection against scratches.

The application of a semi-permanent varnish typically lasts between 30 to 45 minutes, depending on the experience and equipment used.

Removing a semi-permanent varnish is a delicate process. Indeed, this type of formula cannot be removed with a simple conventional remover: its more resilient structure requires the use of an acetone-based product and a specific method. If not done correctly, the removal can weaken the nail, making it thinner, softer, or causing visible ridges. That's why it's generally recommended to have it removed at a salon, although it's entirely possible to remove it at home with caution.

The removal of a semi-permanent nail varnish begins with a gentle filing of the varnish surface to remove the top coat. Each nail is then wrapped in a cotton pad soaked in acetone, held in place by an aluminium foil or a dedicated cap. After about ten minutes, the softened varnish is carefully scraped off with a wooden stick. A light buffing can then be carried out to smooth the nail surface, before applying a nourishing oil to rehydrate the whole nail.

Never attempt to remove your semi-permanent nail varnish by scratching it off with your nails or a metal object. This could significantly damage your nails, which are already weakened by the manicure itself.

Despite its numerous aesthetic benefits, semi-permanent nail varnish is not harmless for the nails. Its composition contains several substances potentially concerning for health. Among them, acrylate derivatives, particularly methacrylates, are most often implicated. These compounds are necessary for the polymerisation of the varnish under UV or LED lamp, but they are also known for their sensitising power. Repeated exposure can lead to contact allergies, with symptoms such as redness, itching, or even eczema localised around the nails. Some varnishes may also contain formaldehyde or toluene, considered as toxic substances at high concentrations.

The removal of semi-permanent nail varnish can also pose issues. Indeed, acetone, necessary for removing this type of varnish, can be particularly drying for the nails and alter their surface as well as the surrounding skin. Moreover, this highly volatile solvent is irritating for the skin, eyes, and respiratory tract. Prolonged exposure, especially concerning those working in beauty salons, can lead to neurotoxic effects, such as headaches, dizziness, or nausea. Finally, beyond the chemical risks, the frequent application of semi-permanent nail varnish can weaken the nails. Even if the product itself does not directly damage the keratin, it's the entire process - application, extended wear, removal - that can make the nails thinner, softer, or more brittle.

To prevent damage to the nails, it is advised to observe periods of rest between two semi-permanent manicures and to leave the nails bare for about two weeks, allowing them to regain their balance.

• DINANI N. & al. Nail cosmetics: a dermatological perspective. Clinical and Experimental Dermatology (2019).

• PAIVA LUZ P. & al. Nail Polishes: A Review on Composition, Presence of Toxic Components, and Inadequate Labeling. Dermatology, Research and Practice (2025).