Asked for female, 21 years old from Hyderabad
There are various treatment for pigmentation. From creams containing hydroquinone to milder ones of Kojic acid, niacinamide, arbutin. There is options of glutathione injections to oral tablets with vitamin C, also laser toning also gives good results. Under arm pigmentation is under hormonal control. Laser toning using Q switch NdYag laser is an option but results variable. You may need 6-8 sessions at 3 weeks gap. It may cost 2-4 thousand per session. Consult a dermatologist.