Talk to Dermatologist on Dark Body Parts

hi. mere friend ki sister ko dark body areas ke bare ma pochna hai. she told me to ask that kia wo dark body areas ke liye aj kal jo creams aye hue ha medicated use kar skati ha ??? such as armpits, dark knees, dark elbows and inner (Vagina) part which is darken than all of the parts of body. usne bataya mai koi home remedy b use kar rahi hun under dark (V) part pe. dahi, turmeric, lemon water, coffee powder or sometimes youghurt ke alternative milk. mask bana ke apply karti hai inhi dark areas per. ap recommend kare ye sab safe hai ??? ya koi medicated creams waghaira hai in parts ko white karne ke liye without any side effects??.