Ringworm is not traditionally classified as a sexually transmitted infection, but the answer is no longer a simple “no.” An emerging fungal strain is spreading through sexual contact, with cases reported in Southeast Asia, Europe, and the United States. The CDC now explicitly acknowledges ringworm infections “linked to intimate or sexual contact,” making this a more complicated picture than it was even a few years ago.
How Ringworm Normally Spreads
Ringworm is a fungal skin infection, not a worm. It spreads easily through direct skin-to-skin contact with an infected person, animal, or contaminated surface like towels, gym equipment, or clothing. You can pick it up at the gym, from a pet, or from sharing personal items. This is why it has historically been grouped with common contagious skin conditions rather than STIs.
Because it spreads through any skin contact, ringworm can certainly pass between sexual partners without sex being the specific route. If your partner has an active infection on their arm or torso, ordinary touching or cuddling could transfer the fungus. Symptoms typically appear 4 to 14 days after your skin contacts the fungus.
The Emerging Sexually Transmitted Strain
A specific fungal strain called Trichophyton mentagrophytes genotype VII (TMVII) is changing the conversation. This strain is directly associated with sexual transmission and was first identified in travelers returning from Thailand after sexual contact with sex workers. More recently, infections have been reported among men who have sex with men in Europe, and the first U.S. case was confirmed in June 2024.
What makes TMVII different from ordinary ringworm is where it shows up and how severe it can be. Infections appear in areas involved in sexual contact: the genitals (the shaft of the penis or skin folds around the vaginal opening), buttocks, groin, and face, along with the trunk, arms, or legs. The CDC describes these infections as potentially “more severe,” and delayed treatment can lead to significant pain, scarring, and secondary bacterial infections.
TMVII can also be tricky to diagnose. It is sometimes confused with psoriasis or other STIs, which delays treatment and gives the infection more time to spread and cause damage.
What Sexually Transmitted Ringworm Looks Like
Ringworm generally produces a circular, red, scaly patch with a raised border and clearer center, giving it the classic “ring” appearance. When it appears in the genital or groin area after sexual contact, the same ring-shaped rash develops, but it may be more inflamed and painful than typical ringworm elsewhere on the body.
The location is the biggest clue. If you develop a new, itchy, ring-shaped rash on or near your genitals, buttocks, or inner thighs shortly after sexual contact with someone who had a skin rash, a fungal infection is worth considering. The 4-to-14-day incubation window means symptoms won’t appear immediately but will develop within about two weeks of exposure.
How Long You’re Contagious
An untreated ringworm infection remains contagious for as long as the rash is present. Once you start antifungal treatment, you’re generally considered contagious for another 48 hours. After that, the risk of spreading it drops significantly, though you should continue treatment for the full prescribed course to clear the infection completely.
For the TMVII strain specifically, treatment tends to be more prolonged than for ordinary ringworm, often requiring oral antifungal medication rather than just a topical cream. If diagnosis is delayed, the infection can worsen and become harder to treat.
Reducing Your Risk
The same principles that prevent other skin-to-skin infections apply here. Avoid direct contact with visible rashes on a partner’s skin. If you or a partner develops a suspicious rash in the groin or genital area, getting it evaluated before resuming sexual contact reduces the chance of spreading it.
A few practical steps help with ringworm prevention in general:
- Keep skin clean and dry, especially in warm, moist areas like the groin and inner thighs where fungi thrive.
- Don’t share towels, clothing, or bedding with someone who has an active infection.
- Wash clothing and sheets in hot water if someone in the household is infected.
- Start treatment early. The sooner you treat a ringworm infection, the sooner you stop being contagious and the less likely you are to develop scarring or complications.
The Bottom Line on Classification
Standard ringworm is not an STI. It spreads through any skin-to-skin contact and through contaminated objects, and most people catch it in completely nonsexual settings. However, the emergence of TMVII has created a category of ringworm that genuinely spreads through sexual contact and behaves more like a traditional STI in terms of how and where it appears. Cases are still relatively uncommon in the U.S. but are being tracked as the strain spreads internationally. If you develop a ring-shaped rash in a genital area after intimate contact, it’s worth mentioning the sexual exposure to your healthcare provider so the right type of testing and treatment can happen quickly.