What drugs can I take to treat a long time dark...

Facial pigmentation or dark spot treatment 
Treatment depends on the cause, and to detect the cause, a medical examination must be carried out and a specialist consulted. For treatment, we advise to stay away from allergens, pay attention to serious nutrition, avoid exposure to harmful sunlight, and stimulate skin moisture by using creams containing aloe vera extract. Creams that contain aloe vera extract can also be used. It contains vitamin C, and treatment can be done by using peeling creams that contain retinoids, or treatment by laser, and if the cause is allergy, Betamethazone ointment can be used twice daily, and if the cause is inflammation, Fuscidin ointment can be used twice daily.
How is the diagnosis made?
By taking the medical history, doing a clinical examination, doing a blood test (CBC) to detect infections, doing a skin allergy test, and taking a biopsy of the affected skin for laboratory diagnosis.
the reasons :
Allergy
inflammation
eczema
vitiligo
immune diseases
poor diet
Genetic factors
aging
smoking
hormonal imbalance
Advice :
We recommend visiting a dermatologist for a medical examination and appropriate treatment according to the cause