The condition u have mentioned could be Trichomycosis. It's , is a bacterial infection of the underarm hairs and in rare cases this infection can also affect pubic hair. It's is not life-threatening, but it can cause some irritation and discomfort. Factors aggravating it could be Humidity, poor hygiene, excessive sweating and obesity.
Woods lamp examination will confirm the same . Consult ur Dermatologist for the same
Health Tips
use a good antifungal powder. Wash ur clothes thoroughly and make sure it's not damp before wearing them