It can be due to hyperpigmentation of the skin. This darkening occurs when an excess of melanin, the brown pigment that produces normal skin color, forms deposits in the skin.
Treatment involves hydroquinone, azelaic acid, corticosteroids, tretinoin cream and laser treatment. Please discuss these options with your dermatologist before using them. For the hair bumps which is due to folliculitis, then waxing even with Brazilian wax will aggravate the condition.Folliculitis and ingrown hair are common even after Brazilian waxing.If you still want to go in for Brazilian waxing ,then apply cold compresses(ice cubes wrapped in a towel) on the rash and take some antihistaminic like benadryl or claritin.You can also apply calamine lotion on the rash.It will help in soothing the skin.A mild corticosteroid cream like dermacort will also help.
Also you can go in for laser hair removal which causes permanent reduction of hair and does not cause folliculitis also.Please consult a good cosmetologist/dermatologist for that.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.