Welcome to Healthcare Magic Forum
You have two issues with your skin,,One is acne corporis with post acne scars...and the other is Hyperpigmentation
Acne is a common human skin disease, characterized by areas of skin with seborrhea (scaly red skin), comedones (blackheads and whiteheads), papules (pinheads), pustules (pimples), nodules (large papules) and possibly scarring. Acne affects mostly skin with the densest population of sebaceous follicles; these areas include the face, the upper part of the chest, and the back.
In your case, you seem to develop acne lesions only over chest and upper arms,..This is a common condition especially in adults,...Some general advise :
Avoid using any kind of moisturising creams/ lotions or oils over the affected area.
Wear cotton clothes as much as possible
Do not use any liquids like dettol/savlon over the affected area
You can however continue to use antibacterial soaps
You might need to apply some antiacne medications like Clindamycin
gel over the affected area along with an agent like benzoyl peroxide
2.5% at night.
But if inspite of the above measures, you continue to develop the lesions, then you might need a course of oral antibiotics
The second issue is that of pigmentation which is due to both post acne scars as well as due to skin tanning
You can start using a lightening agent like kojic acid with vitamin C twice a day. Along with it, you should continously use a sunscreen( spf>26) over your face before going out in the sun..Also take oral vitamin C supplementation continously for a month or so...
If inspite of all these measures, you feel that the pigmentation continues to persisit, then i would advise you to see a dermatologist
who might be able to help you with other techniques like chemical peels
, lasers etc
Hope it helps
Dr Geetika Paul