We all know a whopping great oh-shit-I-can't-sit-down-at-my-desk sore might be worth a trip to the GUM clinic. But what about those let's-wait-and-see-hopefully-it's-nothing symptoms?
These are some of the less obvious signs to look out for. But why not just get tested anyway?
1 Swollen glands
Swollen glands in your neck, groin or armpits can be an early sign of syphilis.
2 Black powder in your underwear
This could be droppings from pubic lice (crabs). Unfortunately, lice can't be prevented by using a condom (they just climb from hair to hair) but they can usually be banished with an insecticide cream. Despite their name, pubic lice can actually live in most body hair but, mercifully, they're not fussed about the hair on your head.
3 Blue spots or spots of blood on your thighs
This could be bites from your lovely lice friends.
4 Stomach ache
Abdominal pain and lower back pain can be a symptom of chlamydia in women.
Conjunctivitis is an eye infection that makes your eyes red, itchy and watery. Developing conjunctivitis can be a sign that your eyes have come into contact with sexual fluids infected with chlamydia. However, conjunctivitis can also be caused by an allergic reaction and other eye problems.
Conjunctivitis usually clears up on its own but if you've been having sex with someone who has chlamydia, then you need to visit a GUM clinic or your GP to get tested.
6 White patches in the mouth
This can be a symptom of more advanced syphilis, along with a blotchy rash, flu-like symptoms, small skin growths that look like genital warts and swollen glands. Typically, the secondary symptoms of the disease develop a few weeks after the initial symptoms of infection.
Primary symptoms usually occur two to three weeks after contracting the disease and include a small, painless ulcer and swollen glands. More on syphilis here.
8 Pain during sex
Pain during sex for women and pain during ejaculation for men is a symptom of a lesser-known STI called Trichomoniasi, an infection caused by a tiny parasite. Painful sex is also a chlamydia symptom in women.
9 Pain while peeing
This can be a sign of herpes, gonorrhoea and chlamydia in both men and women.
For more information on STI symptoms and treatments, visit NHS Choices.
Feature image: iStock