You maybe having a vitamin deficiency. You could get your vitamin B12 level, hemoglobin, folic acid level, vitamin d level and peripheral smear testing done. Other possibility is a condition called Addisonian pigmentation. Another possibility is having developed an allergy to something you come in contact with daily. These are rare and will need to be examined by a dermatologist. Please visit a dermatologist near you so that a diagnosis can be made and you can be treated. Warm regards. Dr. Rajdeep Mysore. Chirag Hospital Bangalore