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Nail enamel or polish is perhaps the most common nail cosmetic. It was introduced in the 1920s when nitrocellulose was developed as a military explosive. Few US plants manufacture nail polish owing to the explosive process of creating nitrocellulose from cellulose fiber, wood pulp, and nitric acid.

The use of nail cosmetics is widespread; there is a nail salon in almost every strip mall in the United States. It therefore behooves dermatologists to familiarize themselves with the products, techniques, and issues associated with the most recently released nail cosmetics.


Dissolving nitrocellulose in an organic solvent produces a hard, glossy film that was adopted by the car industry as a durable shiny paint. Charles Revson saw the potential for nail adornment in this paint in 1930 and formed Revlon in 1932 as a nail polish manufacturing company.

Nail polish contains nitrocellulose and polymers mixed with P-toluenesulfonamide resin, plasticizers, solvents, and pigments. The phthalates that were previously used as plasticizers have been removed from nail polish formulations owing to their ability to function as endocrine disruptors because some people bite their nails and may ingest their nail polish. The North American Contact Dermatitis Group determined that 4% of positive patch tests were due to P-toluenesulfonamide resin. This resin was subsequently removed from hypoallergenic nail polish and replaced with polyester resin or cellulose acetate butyrate. Sensitivity, however, is still possible, and the enamel is less resistant to chipping.

Specialty fillers, such as guanine fish scale, bismuth oxychloride, or titanium dioxide-coated mica, can be added to produce a frosted appearance due to enhanced light reflection. Chopped aluminum, silver, and gold can be added for a metallic shine. Nylon fibers can be added to strengthen the nail. Proteins, gelatins, and vitamins are added in an attempt to beautify the nail plate.


Photochromic Nail Polish

Photochromic nail polish is based on the photodarkening seen in glasses that automatically darken with sun exposure. This kind of nail polish darkens from white to a pinkish color when exposed to the sun. UV light breaks the carbon-oxygen spiro bond, allowing the nail polish to exhibit color when the absorption spectrum shifts to a lower energy state in the visible light range.

Thermochromic Nail Polish

Thermochromic nail polish changes color when exposed to heat or cold based on the temperature of the fingertip and air. When the temperature is below the solvent melting point, hydrogen donation between molecules occurs, leading to rearrangement and the production of color. When the solvent melts with increasing temperature, the molecular interaction stops, and the colorless state reappears.

Magnetic Nail Polish

Magnetic nail polish contains magnetic particles, such as nickel, cobalt, and iron oxide, that align themselves when a magnet is placed over the wet nail polish to create interesting designs.

Crackle Nail Polish

Nails are painted with regular nail polish, and a crackle layer is then painted on top. The nail polish dries unevenly owing to the presence of ethyl alcohol in the crackle layer. This produces cracks in the nail polish. A topcoat of clear nail polish is then applied to prevent chipping.


Currently, gel nails are the most popular form of salon-applied nail color. A long-lasting colored polymer film is placed over the nail. The film is chip resistant, strong, and shiny, but it must be applied and removed professionally. The polymer is applied by dipping the nail into a container filled with spherical polymethyl methacrylate powder, with particles ranging in size from 20 to 60 µm. Moisture trapped within the powder initiates polymerization, or sometimes benzoyl peroxide is used as an initiator. The coating can contain color, glitter, or other materials to create an elaborate appearance.

Figure 1 demonstrates the removal of old gel nail material. An acetone-soaked cotton ball is placed over the nail, and both are wrapped in aluminum foil to soften the old nail polymer. The process dries fingertip skin and the natural nail plate. The softened polymer is removed with a drill (Figure 2), which can thin the nail and roughen its surface. Roughening the nail increases its surface area and thus adherence of the new polymer, but it can also damage the cuticle. Figure 3 shows nails that have been dipped in a copper-colored glittery powder and the application of a liquid initiator on top to create the nail film. Dipping is usually repeated three times to create a thicker, more chip-resistant film. Finally, a drill is used to remove unwanted polymer and shine the nail surface (Figure 4).

Figure 1. An acetone-soaked cotton ball is placed over the nail, and both are wrapped in aluminum foil.

Figure 2. The softened nail polymer is removed with a drill.

Figure 3. A liquid initiator is applied to create the nail film.

Figure 4. A drill is used to remove unwanted polymer and shine the nail surface.


There are several safety issues to consider. Patients who are allergic to methacrylate are likely to experience problems with gel nails unless the technician is careful not to get the unpolymerized methacrylate on their skin. Once the methacrylate is polymerized, it becomes less allergenic. There are no methacrylate-free hypoallergenic nail gels.

The drill used to remove the old nail polymer and shape the new nail polymer can damage the cuticle. Drill bits are not necessarily autoclavable, in which case they may be a source of contamination.

The same container with nail powder is used to dip the fingers of many clients and can also be a source of contamination.


Nail polish is here to stay. Understanding the dermatologic implications of their use can help physicians provide appropriate patient care.

Polymers recently invented for dentistry are finding new uses in the nail industry for innovative and interesting ways to create personal body fashion statements. Stay tuned.

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