Let’s skip the awkwardness and get straight to what matters. Sexually transmitted infections — more commonly known as STIs — are a normal part of sexual health. They’re not a sign of being irresponsible, and they’re certainly not something to be ashamed of. What they are, however, is something worth knowing about. Because the single biggest risk with most STIs is not knowing you have one.
This guide walks you through the most common STIs, what their symptoms look like, and — crucially — what to do if you think something might be wrong. Whether you’re experiencing something unusual or just want to be better informed, you’re in the right place.
Why Knowing STI Symptoms Matters More Than You Think
Here’s the thing that catches most people off guard: a large proportion of STIs cause no obvious symptoms at all. That means you could have an infection, pass it on to someone else, and experience no discomfort whatsoever. In some cases, infections left untreated for months or years can cause serious long-term complications—including infertility, chronic pain, and, in rare cases, life-threatening illness.
Being aware of the symptoms isn’t about living in fear — it’s about being empowered. Knowing what to look for means you’re more likely to catch something early, get treated quickly, and protect both yourself and your partners.
💡 Many STIs are completely curable when caught early. Even those that can’t be cured — like herpes or HIV — are highly manageable with the right treatment. Early detection always leads to better outcomes.
Common STIs and Their Symptoms
Below is a breakdown of the most prevalent sexually transmitted infections and the signs associated with each. Keep in mind that symptoms can vary significantly between individuals, and some people will experience none at all.
Chlamydia
Chlamydia is the most commonly diagnosed STI in many countries, particularly among people under 25. It’s a bacterial infection passed through unprotected vaginal, anal, or oral sex, and the majority of people who have it experience no symptoms at all.
Possible symptoms include:
- Unusual discharge from the penis, vagina, or rectum
- Burning or pain when urinating
- Pain or swelling in the testicles (in men)
- Pelvic or lower abdominal pain (in women)
- Bleeding between periods or after sex (in women)
- Rectal pain, discharge, or bleeding if contracted anally
Because chlamydia is so often silent, regular testing is the only reliable way to know your status. It’s easily treated with a short course of antibiotics.
Gonorrhoea
Gonorrhea is another bacterial infection spread through sexual contact. Like chlamydia, it can affect the genitals, rectum, and throat. Symptoms, when they appear, tend to show up within two weeks of exposure.
Possible symptoms include:
- Thick, green or yellow discharge from the penis or vagina
- Pain or burning sensation when urinating
- Inflammation or swelling at the tip of the penis
- Increased vaginal discharge or bleeding between periods
- Rectal discomfort, discharge, or bleeding
- Sore throat if contracted through oral sex
Gonorrhoea is treatable with antibiotics, though antibiotic-resistant strains are becoming increasingly common—another reason why early diagnosis and proper treatment are so important.
Genital Herpes (HSV-1 and HSV-2)
Herpes is caused by the herpes simplex virus and is extremely widespread. HSV-1 typically causes oral herpes (cold sores), while HSV-2 is more commonly associated with genital herpes— though either strain can affect either area. Many people with herpes have never had a recognizable outbreak.
Possible symptoms include:
- Small blisters or sores around the genitals, buttocks, or thighs
- Tingling, itching, or burning before sores appear (known as a prodrome)
- Pain or discomfort when urinating if sores are near the urethra
- Flu-like symptoms during the first outbreak (fever, aches, swollen glands)
- Recurring outbreaks triggered by stress, illness, or hormonal changes
Herpes cannot be cured, but antiviral medications can significantly reduce the frequency and severity of outbreaks and lower the risk of transmission to partners.
Syphilis
Syphilis is a bacterial infection that progresses through distinct stages, each with different symptoms. It’s been rising in prevalence in many countries recently, making awareness particularly important.
Stages and symptoms:
- Primary stage: A painless sore (chancre) at the site of infection — genitals, anus, lips, or mouth
- Secondary stage: Skin rash (often on palms and soles), flu-like symptoms, mouth sores
- Latent stage: No visible symptoms, but the infection remains active in the body
- Tertiary stage (rare): Serious damage to the heart, brain, and other organs if untreated
The painless nature of the primary sore means syphilis is frequently missed. A simple blood test can diagnose it, and early stages are curable with antibiotics.
HPV and Genital Warts
Human Papillomavirus (HPV) is the most common sexually transmitted infection worldwide. Most strains cause no symptoms and clear on their own. However, certain strains cause genital warts, while others are associated with cervical and other cancers.
Genital warts may appear as:
- Small, flesh-coloured or grey bumps in the genital or anal area
- Clusters of growths with a cauliflower-like appearance
- Flat lesions that are barely visible to the naked eye
- Itching, discomfort, or occasional bleeding in the affected area
The HPV vaccine offers strong protection against the most harmful strains. For more detail on what early HPV warts look like in women, see our dedicated guide on early-stage HPV warts in females.
HIV
HIV (Human Immunodeficiency Virus) attacks the immune system and is transmitted through unprotected sex, sharing needles, or from mother to child during birth or breast-feeding. While there is no cure, modern antiretroviral therapy (ART) allows people with HIV to live long, healthy lives — and an undetectable viral load means the virus cannot be passed on sexually (U=U: Undetectable = Untransmittable).
Possible early symptoms (within 2–4 weeks of exposure):
- Fever, chills, and night sweats
- Swollen lymph nodes in the neck, armpits, or groin
- Sore throat and mouth ulcers
- Skin rash — often on the chest or back
- Muscle aches, joint pain, fatigue, and headaches
These early symptoms—known as acute HIV infection—can be mistaken for a bad flu. After this stage, HIV may cause no symptoms for years. Regular testing is essential for anyone sexually active with multiple partners or who has had unprotected sex.
Trichomoniasis
Trichomoniasis is caused by a tiny parasite and is one of the most common curable STIs globally. It most often affects the vagina and urethra. Around 70% of people with trichomoniasis have no symptoms at all.
When symptoms do occur, they may include:
- Yellow-green or frothy vaginal discharge with an unpleasant odour
- Itching, burning, or soreness around the vagina
- Pain during sex or urination
- In men: irritation inside the penis, burning after urination or ejaculation
Trichomoniasis is easily treated with antibiotics, and both partners should be treated simultaneously to prevent reinfection.
Symptoms That Should Never Be Ignored
While many STIs are silent, certain symptoms should always prompt you to seek medical attention promptly:
- Any unusual discharge from the genitals — changes in colour, consistency, or smell
- Sores, blisters, ulcers, or unusual growths in the genital, anal, or oral area
- Pain or burning when urinating
- Pain during sexual intercourse
- Unexplained rashes, particularly on the palms, soles, or torso
- Persistent pelvic or lower abdominal pain
- Swollen lymph nodes in the groin area
- Unexpected bleeding between periods or after sex
Even if you’re not experiencing any of these, regular STI screening is strongly recommended for anyone who is sexually active — particularly if you have multiple partners, have recently started a new relationship, or have had unprotected sex.
How Are STIs Diagnosed?
The good news is that testing for most STIs is quick, straightforward, and widely available. Depending on the infection being tested for, a clinician may use a blood test, urine sample, swab from the genitals, throat, or rectum, or a physical examination.
Many sexual health clinics offer confidential testing with fast turnaround times. At-home testing kits are also available for several common infections including chlamydia, gonorrhoea, HIV, and syphilis. For guidance on how often you should be screened, check out our complete STI testing schedule guide.
What to Do If You Test Positive
A positive result can feel frightening, but it’s important to keep perspective. Most STIs are easily treated, and even those that aren’t curable are entirely manageable. Here’s what to do:
- Follow your doctor’s prescribed treatment course — and complete it fully, even if symptoms improve
- Inform recent sexual partners so they can get tested and treated if necessary
- Avoid sexual contact until you and your partner(s) have completed treatment
- Return for a follow-up test if recommended by your healthcare provider
- Review your sexual health practices going forward — use protection consistently and test regularly
For practical advice on reducing the risk of transmission — including barrier methods and vaccination — read our guide on how to prevent the spread of genital warts and other STIs.
Final Thoughts
Understanding STI symptoms is one of the most empowering things you can do for your sexual health. It means you’re more likely to catch something early, less likely to unknowingly pass it on, and better equipped to have honest conversations with partners and healthcare providers.
There’s no shame in getting tested — in fact, it’s one of the most responsible things a sexually active person can do. If anything in this guide has made you think twice, that’s exactly the point. Book that appointment. Take that test. Your health is worth it.