Dark underarms and inner thighs can be quite a concern for many of my patients.
A combination of in- clinic treatments with topical de-pigmentation creams can help to lighten the underarm and inner thighs.
In- clinic treatment can include pigment lasers (Q-Switch NDYag) and/or chemical peels to lighten these areas. Depending on your skin, typically, quite a few sessions (up to 5-10) may be required to get good results.
Yes, as mentioned by Dr Ho, home remedies that contain acids may also cause irritation and inflammation that may worsen the dark patches in these areas so do be careful.
Hope that helps!