There are many studies confirms that Vitamin K can reduce under eye dark circles if used externally as it will reduce dark circles by replacing dead blood cells. As their are several reasons for dark circle development like Genetics, Lack of sleep, Dehydration, Chemical irritation so you need to correct reason of behind dark circle generation.
Vitamin K can be even more effective for those dark circles when combined with vitamin A in a cream. Topical application of a gel containing a derivative of vitamin K, as well as vitamins A, C, and E, was effective in reducing dark under-eye circles while also decreasing wrinkles.
Vitamin K creams work slowly so you need to apply vitamin k cream for extended periods.