Gel and shellac manicures are all the rage right now- and I personally know why- they look great, dry instantly and last longer than regular polish. However, these types of polish require light to harden/set and many salons use small UV light sources, which raises the question of skin cancer safety.
This type of salon service is relatively new, so it will be many years before we really know if there is an increased risk of skin cancer. A recent article in a dermatology journal had the opinion that the risk is minimal. I feel that UV exposure at the salon is completely unnecessary. It has a risk of cancer (even if it is small) and causes photo-aging (this means ugly brown spots). LED lights can be used and give the same results (great nails) without any UV exposure. I had one manicure with UV and noticed a sun spot on the top of my hand. That was my first and last manicure at a salon that used UV light.
Bottom line- If you want to try gel or shellac, look for a salon that uses an LED light source.