Sexually transmitted infections (STIs) are often associated with genital itching or burning, but symptoms can appear in far less obvious places. With 402,000 new STI diagnoses in 2025, experts are highlighting the unexpected body parts where signs may manifest. Abbas Kanani, superintendent pharmacist at Chemist Click, notes that “STIs don’t always follow the textbook pattern people expect.” He adds that infections can affect different parts of the body depending on the type and transmission route, and shouldn’t automatically be ruled out as unrelated to sexual health.
Rashes on Palms and Soles
A rash on the palms of the hands can be a later symptom of syphilis, especially if the infection has been left untreated. Pharmacist Thorrun Govind explains that “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 vary significantly from person to person. While syphilis is not transmitted through hand-to-hand contact, it can be caught by touching an infected fluid-filled sore called a chancre.
The soles of the feet can also be affected by the characteristic rash of secondary syphilis, which may spread across the body and be subtle enough to go unnoticed. Abbas Kanani advises that “a rash on the feet is easy to put down to something like athlete’s foot or irritation from footwear,” but if an unusual rash appears on both palms and soles, especially alongside other unexplained symptoms, it’s worth getting checked. A rash coinciding with swollen glands, tiredness, or unprotected sex should prompt a visit to a sexual health clinic for an STI test.
Eye and Throat Infections
Gonorrhoea can reach the eye if infectious genital fluid is transferred by the hands, according to Thorrun Govind. This can cause redness, pain, and discharge, and may lead to gonococcal conjunctivitis, a serious condition requiring 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. Thorrun explains that “infections such as gonorrhoea, chlamydia, syphilis, herpes and HPV can all affect the throat.” Abbas Kanani acknowledges that a sore throat is more commonly caused by a respiratory infection, but sexual contact can expose the throat to certain infections.
Joint Pain and Mouth Sores
Some STIs can spread to the joints, leading to painful, stiff, or swollen joints. In rare cases, gonorrhoea can spread to the bloodstream and joints, and other STIs can trigger reactive arthritis. Abbas Kanani says that “unexplained joint pain isn’t something most people would immediately associate with an STI,” but if joint symptoms appear alongside a rash, eye problems, urinary symptoms, or other signs of infection, medical advice is warranted.
The mouth and lips are vulnerable to STIs from oral sex, particularly if there are cuts or broken skin. Syphilis can cause painless sores in the mouth and lips, which may go unnoticed. Abbas notes that “a persistent or unusual sore, particularly after sexual contact with a new partner, shouldn’t simply be ignored,” as syphilis sores can be painless.
Anal and Rectal Symptoms
Gonorrhoea and chlamydia can infect the rectum, causing discharge, soreness, itching, bleeding, or pain during bowel movements, though many infections produce no symptoms. Abbas Kanani encourages people to mention anal symptoms despite potential embarrassment, adding that “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.”
