There are many causes of dark skin between thighs that might extend this skin discoloration problem to the groin or other bikini areas. Here I list a few of the common ones and how to combat the problem.
People who are obese have often been found to have the dark skin inner thigh problem since their thighs rub against each other as they are walking or exercising. Rubbing thighs “can cause discoloration and itchy skin, a condition called chaffing”
To avoid this problem, always wear pants that are loosely fitting and avoid synthetic fibers including nylon as they cause more irritation. Go for pants made from natural fibers especially cotton.
Excess friction and sweating between thighs can darken or blacken them. Furthermore, if you are fond of wearing very tight clothing, you will only be worsening this problem. Therefore, wearing loose breathable clothing might help if this is the cause in your unique case. Furthermore, avoid dark colored tight jeans.
Hormonal imbalance is a common cause of black inner thighs to some women. You can easily tell that the cause is a hormonal imbalance if they darken during some stages when there is a lot of hormonal changes such as during your monthly cycles, lactation or pregnancy.