No its not particularly bad for your nails, hands or feet. When you have a 3 week polish it is best to use a cuticle oil regularly, ideally 2-3 times a day but as often as you remember! This feeds the nails and keeps them strong while the polish is on. The polish itself will not harm your nails, the removal process often uses acetone which can dry the nails and nail beds out so make sure your technician only applies acetone to the nail polish rather than dipping your hands in the acetone. Ask yur technician about the nest oil to use, I recommend Solar Oil as I use the CND Shellac system.