Sexually transmitted infections (STIs) can produce symptoms in unexpected parts of the body, not just the genitals, according to pharmacists. With 402,000 new STI diagnoses in 2025 alone, experts are highlighting less obvious signs that might indicate the need for a sexual health clinic visit.
Unusual places STI symptoms can appear
“STIs don’t always follow the textbook pattern people expect,” says Abbas Kanani, superintendent pharmacist at Chemist Click. “It can affect different parts of the body depending on the type of infection and how it has been transmitted, and it shouldn’t automatically be ruled out as having nothing to do with your sexual health.”
A rash on the palms of the hands can be a later symptom of syphilis, sometimes spreading across the body if the infection is left untreated. “Syphilis is one of those infections that can present in ways people simply would not associate with an STI,” pharmacist Thorrun Govind tells Metro. “Later symptoms can include a rash on the palms of the hands which isn’t usually itchy, but it can be mistaken for a number of more familiar skin conditions like eczema, psoriasis or an allergic reaction.” The rash can look different from person to person. While syphilis cannot be caught from hand-to-hand touching, it can be caught from touching an infected fluid-filled sore called a chancre.
Feet, eyes, and throat
The soles of the feet can also be affected by the characteristic rash seen during secondary syphilis. “A rash on the feet is easy to put down to something like athlete’s foot or irritation from footwear,” Abbas explains. “But if you notice an unusual rash on both the palms and soles, particularly alongside other unexplained symptoms, it’s worth getting it checked rather than assuming it’s simply a skin problem.” A rash coinciding with swollen glands, tiredness, and unprotected sex should prompt an STI test.
Gonorrhoea can reach the eye if infectious genital fluid is transferred there by the hands, causing redness, pain, and discharge. Thorrun adds that this can lead to gonococcal conjunctivitis, which requires urgent medical attention to prevent permanent eye damage. Untreated syphilis can also affect the eyes, causing pain, redness, and vision changes. The throat can be exposed to STIs through oral sex, with infections such as gonorrhoea, chlamydia, syphilis, herpes, and HPV all potentially affecting it. Abbas notes that a sore throat is more likely due to a common respiratory infection, but sexual contact can expose the throat to certain infections.
Joints, mouth, and anus
In rare instances, gonorrhoea can spread to the bloodstream and joints, and other STIs can prompt reactive arthritis, leading to painful, stiff, or swollen joints. “Unexplained joint pain isn’t something most people would immediately associate with an STI,” says Abbas. “But, if joint symptoms develop alongside a rash, eye problems, urinary symptoms or other signs of infection, it’s worth seeking medical advice.”
The mouth and lips are vulnerable to STIs from oral sex, especially if there are cuts, sores, or broken skin. “The risk can be higher if there are cuts, sores or broken skin in or around the mouth, because this can provide an easier route for infection,” Thorrun adds. Syphilis can cause painless sores in the mouth and lips, sometimes without obvious genital symptoms. “A persistent or unusual sore, particularly after sexual contact with a new partner, shouldn’t simply be ignored,” Abbas says. “Syphilis sores can be painless, which means people may not recognise them as a sign of infection.”
Gonorrhoea and chlamydia can also infect the rectum, causing discharge, soreness, itching, bleeding, or pain when passing stool, although many infections cause no symptoms. “People can feel embarrassed talking about symptoms affecting the anus, but they’re important symptoms to mention,” Abbas says. “Some infections in this area cause no noticeable symptoms at all, so testing is particularly important following unprotected anal sex or if you’ve been told a partner has an STI.”
