These products can be used underneath gel polish, but it is important to note that using gel, depending on its ingredients, can cause damage to the nail plate no matter how you prepare the surface. Dr. Adigun recommends prepping the nail with an emollient that will hydrate the nail prior to painting them. Then use a 3-free polish to avoid any harsh chemicals that could irritate the skin. “3-free polish means it is polishes that are made without formaldehyde, toluene, and dibutyl phthalate,” she says. “Those are the big problematic ingredients known to cause an irritant reaction and an allergic reaction to the nail and the skin around the nail.” Upon removing the gel polish, Dr. Adigun advises patients to use an acetone-free nail polish remover, noting that it is one of the most harmful chemicals to apply to nails.