I have very dark inner thigh and I'm not as dark. Would a 20% TCA one layer chemical peel be a good idea to start with?

This is difficult to tell without pictures and needs an in-person evaluation. Hyperpigmentation needs a combination approach to get improvement. This can be improved with a combination of lasers, Aerolase, microneedling/prp, skin lightening, peels, and skin care. Sun protection is essential. I recommend getting a formal evaluation with a cosmetic dermatologist. Best, Dr. Emer

No type of skin peel in medial thighs will give you any lasting depigmentation.   You will in fact likely pigment more.   See a plastic surgeon and try skin lighteners and also condider trying the Picosure laser treatments.   This will take a lot of time for success.   My Best,  Dr Commons   

You do need a diagnosis before treatment. You may have acanthosis nigricans or even constitutional darkening, post inflammatory skin darkening etc.. Diagnosis before treatment. A 20% TCA peel is not advisable, way too strong. If its AN, then possibly Vitamin A creams or peels are less irritating and possibly more effective. Dr Davin S. Lim. Brisbane. Australia.