How to reduce swelling under the eyelid after restylane injection?

The eyelid tissue is the thinnest on the entire body, because of this, swelling is commonly observed. To reduce swelling, I generally recommend limiting one's salt intake for three days before the treatment and for 1-2 days after the treatment. Avoiding aspirin, advil, etc for two weeks before the treatment will help to decrease bruising which can create swelling.  If one encounters swelling after juvederm or restylane treatments, ice for 48 hours may help, followed by moist heat. If swelling persists beyond 3 weeks, I would suggest following up with your doctor to see if the area would benefit from some hyaluronidase to dissolve some of the filler.

Swelling and bruising is very common after treating the tear troughs, you can continue using arnica and cold compresses but the most important thing is giving it time to heal 

While all areas tend to swell to some degree after injections, the eye area is particularly susceptible to swelling.  When we do injections, I hold pressure on the area if I see any evidence of a bruise or swelling.  This really does help a bit. For now, I would rely on antihistamines and you will probably have to wait it out.  In the future, you should also avoid any bending over or straining within hours of injections and definitely avoid workouts for a day or so!  Good luck!