I think you may be having contact dermatitis to the home remedy you are using. Having said that there are lot other causes of facial melanosis like excess exposure to sunlight or use of perfume or cosmetics.
Next Steps
Pls visit a dermatologist near you for proper examination and treatment.
Health Tips
in the meanwhile Pls start using suncros gel 30 spf sunscreen 3 times daily 8 am 11 am and 2 pm. regards