A closer look at semi-permanent nail polish.

Semi-permanent nail polish is a long-lasting polish with enhanced shine that can last up to three weeks. This type of polish helps avoid the frustration of seeing your nail color chip just a few days after your manicure. Unlike the very liquid texture of a standard nail polish, the texture of a semi-permanent polish 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 nail polish ensures colored and shiny nails for an extended period.

When examining its formulation, the semi-permanent nail polish is composed of photosensitive acrylic resins. Unlike traditional nail polishes that dry in open air, semi-permanent polish only hardens under the influence of a UV or LED lamp, through a process called photopolymerization. This chemical reaction transforms the oligomers present in the formula into a rigid polymer network, thus creating a smooth, solid, and adherent 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 polish is almost like that of a traditional polish 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 polish adherence. Then, push back the cuticles with a wooden stick and thoroughly degrease the nails with a cotton ball soaked in nail polish remover. This ensures a good hold of the nail polish.

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

The application of a semi-permanent polish typically takes about 30 to 45 minutes, depending on the experience and equipment used.

Removing a semi-permanent nail polish is a delicate process. Indeed, this type of formula cannot be removed with a simple traditional nail polish remover: its more resilient structure requires the use of an acetone-based product and a specific method. If not done properly, 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 polish begins with a gentle filing of the polish surface to remove the top coat. Each nail is then wrapped in a cotton ball soaked in acetone, held in place by an aluminum foil or a dedicated cap. After about ten minutes, the softened polish is carefully scraped off with a wooden stick. A light buffing can then be performed to smooth the nail surface, before applying a nourishing oil to rehydrate the entire nail.

Never attempt to remove your semi-permanent nail polish 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 polish is not harmless to 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 polymerization of the polish under UV or LED lamp, but they are also known for their sensitizing power. Repeated exposure can lead to contact allergies, with symptoms such as redness, itching, or even localized eczema around the nails. Some polishes may also contain formaldehyde or toluene, considered as toxic substances at high concentrations.

The removal of semi-permanent nail polish can also pose issues. Indeed, acetone, which is necessary for removing this type of polish, can be particularly drying for the nails and can alter their surface as well as the surrounding skin. Moreover, this highly volatile solvent is irritating to the skin, eyes, and respiratory tract. Prolonged exposure, especially concerning those working in salons, can lead to neurotoxic effects, such as headaches, dizziness, or nausea. Finally, beyond the chemical risks, the frequent application of semi-permanent nail polish 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 nail damage, it is advised to observe rest periods between semi-permanent manicures and to leave 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).