Some STIs can be spread by sharing cloth material such as clothing and bedding, but many cannot. Herpes, syphilis, and HIV are not usually spread via clothing, sheets, or towels.
Bacterial vaginosis (Bacterial vaginosis is a type of vaginal inflammation caused by the overgrowth of bacteria naturally found in the vagina, which upsets the natural balance ) is not caused by shared bedding or clothing, but using wet towels or bathing suits, in general, may lead to the bacterial imbalances that cause bacterial vaginosis. Trichomoniasis (Trichomoniasis is a common sexually transmitted infection caused by a parasite) can be spread via damp clothing or towels.
Although rare, pubic lice can be contracted via shared bedding and clothing. Prolonged exposure to contaminated clothing can lead to the spread of HPV.
Materials infected by the discharges caused by chlamydia can transmit the infection to other people. This is especially common when chlamydia infects the eyes.
Diseases like pediculosis (pediculosis is best made by finding a live nymph or adult louse on the scalp or in the hair of a person) which is considered to be most contagious sexually transmitted disease among all easily spreads through sharing of towels.
Pediculosis is caused by crab louse. These parasites deposit their eggs at the base of hair follicles and the person using the same towel are at higher risk of getting the disease. The infection causes itching and social embarrassment.
Another disease which can be transmitted through use of towels is scabies. It is caused by itch mite and causes severe itchy skin on the elbow, wrist and buttocks. Itching is severe at night time.
You are advised to wash your towels often with warm water. Do not share your towels with anyone.