Some skin care ingredients that are promoted as anti aging can be usefull for young skin too. Anti-oxidants will protect against UV damage something that is much the same at the age of 17 as at 67. For example Green tea extract will protect both against UV radiation and help keep your pores from getting clogged. At 17 skin is very resilient and will quickly bounce back from all most any stress it has been exposed to, still some substances can be useful to help recover from skin conditions that has left marks, like acne scarring, any type of scarring really. These ingredients include rose hip oil, omega 3 oils, different peptides, some of the vitamin B's, anti oxitads like that of green tea, tomato, sea weed extracts. These are also heavily promoted as anti-wrinkle agents. The theory is that nurishing skin from the outside gives the skin more to work with and aids all its normal functions. There are luckily very few ingredients that are suspeced of causing cancer, and most of them are used as preservatives. There are no good reasong why a 40 year old should be exposed to more possible carsinogens than a 17 year old. Though I admit that the most invasive procedures to combat wrinkles and sagging skin are on the risky side.