Hello,
Thanks for writing your query to us.

Shaving causes hair to grow back thicker and darker, and this dark hair is often visible under transparent, light skin - which is what makes the skin look darker. Also, waxing removes dead skin, while shaving does not do the same. If you shave underarms regularly, you may want to scrub your underarm area with a pumice stone on a daily basis. This should help combat darkness to an extent. Apply lemon juice. Don't wear polyester clothing near those areas. Wash regularly, make sure these areas are dry by applying powder. Try Shower to Shower. Wax these areas regularly. If your inner thighs rub together this also causes it to go dark, so you may need to lose weight on your thighs.

Stop using hair removal cream on your underarms and start waxing. Scrub your underarms daily with a pumice stone, after applying soap, while taking a shower.
Take care.

Hi Tanisha,
Dark armpits and thighs could be due to friction,excessive weight gain, excessive sweating, use of depilatory creams , shaving or use of antiperspirants and it could also be due to acanthosis nigricans. So in general the causative factors should be avoided i.e.
Reduce weight if you are obese
Do not shave or use hair removers instead wax the area or get laser hair reduction done
Do not use deodorants or antiperspirants
To treat the pigmentation one can use lightening creams like skin lite or Glycolic acid based creams. One can also go with chemical peel sessions with Glycolic acid, trichloro acetic acid or salicylic acid peels. You can also use home remedies along with medical treatment like using chickpea flour along with turmeric and lemon. Mix a little bit of milk or cream, make a paste and use it thrice in a week over dark areas. Hope that answers your query
Regards,
Dr kalpana