it's safe to do Fat Transfer for under eyes for dark circles in age of 21
Is it Safe to Have Fat Transfer Under the Eyes for Dark Circles?
Doctor Answers 3
Fat Transfer Under Eyes - Safe if Plastic Surgeon is Experienced
Without more history or at least a photo this is tough to answer. If the "dark circles" are caused from shadowing from a depression then this is a good technique if done by experienced plastic surgeons.. The problem is that if the injections are not done deeply, close to the underlying bone or is inadvertently injected just below the skin or in the muscle they may cause lumps or nodules. I personally like this technique and perform it often with good results.
If the dark circles are familial or from hyperpigmentation then fat transfer will not directly improve your appearance.
Choose your plastic surgeon wisely on this one, ask how many time they have performed this technique and make sure they are board certified.
Fat injections under eyes for dark circles.
This is not a good idea. Dark circles are caused by several problems. Fat injections cause lumps quite often. If fat is transferred with a blepharoplasty it works well without lumps.
Fat grafting for lower eyelid circles
The best treatment for under eye dark circles depends on the cause. In some people the skin has darker pigmentation in the area which is quite hard to treat.
In other the dark coloration is from shadowing from facial volume loss. At your young age I would be reluctant to place fat in the area, though. Skin fillers such as restylane can be done at your age. Make sure you find an experienced surgeon to treat this area.