There are various causes for facial pigmentation. Which can be sunlight exacerbated, allergy to hair dye or other cosmetic products used, hyper pigmentation disorders like melasma, lichen planus pigmentosus, acanthosis nigricans, fixed drug eruption, rhiel's melanosis.. Hence a personal consultation and proper evaluation would be advisable. Using a dermatoscopy (which has a 20x magnification) the dermatologist can better examine and assess the condition. Hence, I would recommend getting a personal consultation for your problem.
Next Steps
Meet with a dermatologist for a thorough evaluation.