For the doctor to allow you to have under-eye fillers, you should be at least 18 years old for legal and safety reasons. However, some countries have medical regulations which only allows individuals 21 and older to have the treatment done. Although, some doctors do not allow fillers for those aged below 30 years old since the skin can still retain its plumpness. They recommend that an individual below 30 only undergo a filler treatment when the need arises like dramatic signs of premature aging.