Gel polish contains small molecules called monomers. When you put your hand under the ultraviolet (UV) nail lamp, the UV radiation triggers a chemical reaction that causes the monomers to link together to form long polymer chains, setting the gel. The result is a tough, flexible nail polish.
In 2009, US researchers sparked concern with an article describing how two nail bar regulars had developed skin cancer on the backs of their hands. However, the researchers weren’t able to make any strong conclusions about whether the UV nail lamps were responsible, and a separate 2018 review of the literature concluded that the cancer risk from nail lamps is low. Nevertheless, the authors of the review recommend using fingerless gloves or sunscreen to protect the hands while under
Finally, the nail filing that occurs before the polish, and the soaking in acetone to remove gel nails, can make nails more brittle and likely to split. So treat yourself, but it might be worth planning in some gel-free periods, and protecting your hands.