I have brown mark under my eyes it happened after allergic reaction with lotion will it fade on its own?

Any inflammation can increase local pigmentation and such pigmentation will fade with time. It may take longer than you may like. Apply sunscreen to the affected area will help. In the interim, judicious use of makeup would cover up the pigment. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless. Get HPV vaccine.