Collagen supplements are a current fad, thanks to epidemiologists abusing statistics. No one is better at that than the Harvard TS Chan School of Public Health, the American 'Mecca of Woo.'  Hardly a week goes by without them endorsing some new miracle vegetable or diet, or trying to scare people about a trace chemical. 

Yet even Harvard notes that collagen is a useless supplement with no clinical trials, just industry marketing campaigns similar to organic food and coffee enemas.

It can't harm you, collagen is naturally found in meat and fish. And if you are on a vegan or some other alternative fad diet, you do need to worry about your health, including collagen, but pills and creams won't be biologically available. 

If someone calms otherwise, it's not science, it's plain old capitalism. These things are everywhere but only because the Clinton administration gave supplements and alternative medicine a free pass from real FDA scrutiny. If you're rich, go for it, it won't help you but it won't hurt either. If you are not, spend your money more wisely.