It has antioxidant, skin soothing and restorative properties. 

Studies have shown that a lipid-based delivery system is best for quercetin's antioxidant benefits. This type of formula produces an initial burst of quercetin accompanied by a 24-hour timed release. 

A study also found that adding quercetin to sunscreens helped stabilise the otherwise unstable chemical UV filters avobenzone and octinoxate against degradation – and it performed better than traditional stabilisers like octocrylene and vitamin E.

See also:
Flavonoid
Antioxidant