Itching, soreness or unusual discharge down below? It's natural to worry it's an STI. But chlamydia, herpes and thrush are three very different infections, and each one needs a different treatment. So is it thrush or herpes, chlamydia, or something else entirely?
Here's how to tell the difference between chlamydia, herpes and thrush, what causes each one, and why getting a proper diagnosis matters.
Similar symptoms, different causes. Knowing which infection you have is the first step to clearing it up.
What's the difference between chlamydia, herpes and thrush?
The quickest way to tell them apart is by what causes them:
- Chlamydia - a bacterial STI, treated with antibiotics
- Genital herpes - a viral STI, managed with antiviral medicine
- Thrush - a yeast infection that isn't an STI, treated with antifungal medicine
That's why the cause matters so much. Antibiotics clear bacteria, but they do nothing against a virus or a yeast.
What is chlamydia?
Chlamydia is a bacterial infection passed on through unprotected sex. It's the most commonly diagnosed STI in England.1
Here's the tricky part. Most people with chlamydia don't notice any symptoms at all. At least 70% of women and half of men with it have no symptoms.2
If symptoms do show up, they can include:
- Pain when peeing
- Unusual discharge from the vagina, penis or bottom
- Pain in the tummy, or bleeding after sex or between periods, in women
- Pain and swelling in the testicles in men
Chlamydia is usually treated with a week-long course of the antibiotic doxycycline.2 You should not have sex, including oral sex, until you and your partner have both finished treatment.2
No symptoms doesn't mean no infection. If you've had unprotected sex with a new partner, a test is the only way to know.
What is genital herpes?
Genital herpes is a viral STI caused by the herpes simplex virus, type 1 or type 2.3 It's passed on through skin-to-skin contact, including vaginal, anal and oral sex.4
Symptoms can include tingling, burning or itching, followed by small blisters that burst and leave red, painful sores. Peeing can hurt too. The first outbreak can also come with flu-like symptoms.5
Symptoms don't always appear straightaway. They can take weeks or even years to show up after you've caught the virus.3
There's no cure for genital herpes. But antiviral tablets like aciclovir and valaciclovir can ease an outbreak. Outbreaks that come back are usually milder than the first one.3
If you get herpes treatment through Pharmica, a prescriber will check it's suitable for you first, including whether a GP or sexual health clinic has diagnosed herpes before. If your symptoms do not improve after 7 days of treatment, you must see your doctor.
Herpes is very manageable. Starting antivirals at the first tingle gives them the best chance of easing an outbreak.
What is thrush, and is it an STI?
Thrush is a common yeast infection caused by a fungus called Candida. It isn't an STI. It can occasionally pass between partners during sex, but this is uncommon.6
In women, it usually causes a thick, white discharge, along with itching, soreness and stinging when you pee or have sex. In men, it tends to cause redness, itching and a lumpy discharge under the foreskin.6
Things that can trigger thrush include:7
- Taking antibiotics
- Perfumed soaps and vaginal washes
- Tight nylon or lycra underwear
Thrush is treated with antifungal creams, pessaries or tablets, and should clear up within 7 to 14 days.8 Some antifungal creams can weaken condoms and diaphragms, so they may not protect you as well during treatment.8 Your partner usually doesn't need treatment unless they have symptoms too.9 It's best to avoid sex until the infection has cleared.6
Thinking of getting fluconazole for thrush through Pharmica? Our service is for people who've had genital thrush diagnosed by a doctor before. It can't supply it if you've had an STI or may have been exposed to one, or if you have stinging when you pee, so get checked at a GP or sexual health clinic first. That doesn't make thrush an STI. It just means another cause needs ruling out.
Using an antifungal cream and condoms? You may need extra protection until your treatment is finished.
Is it thrush or herpes?
Thrush and genital herpes can both cause itching and soreness, so they're easy to mix up. The biggest clue is what you can see.
Herpes usually causes small blisters that burst and leave painful sores.5 Thrush tends to cause redness and a thick, white discharge, without blisters.6
Still not sure? A sexual health clinic can look at your symptoms and choose the right tests. Herpes is usually tested with a swab from a fresh blister or sore.3 Chlamydia testing may use a urine sample or a vaginal swab.10
Is it thrush or a UTI?
Urinary tract infections (UTIs), including cystitis, are something else again. They're usually caused by bacteria getting into the urinary tract, rather than being passed on through sex like an STI.
Thrush can cause stinging when you pee, which is easy to mistake for a UTI.6 Itching and a thick, white discharge point more towards thrush. If you're not sure which it is, a pharmacist can help you work it out.
When should you get checked?
The symptoms of these infections overlap a lot, so it's hard to tell which one you have just by looking. The best thing to do is get tested before you start any treatment.
You can get tested at a sexual health clinic or through your GP. See a GP or pharmacist if:8
- You have thrush symptoms for the first time
- Thrush keeps coming back or treatment hasn't worked
- You're pregnant or breastfeeding
- You're under 16 or over 60
If you're diagnosed with chlamydia, the clinic will advise on testing and treatment for your recent sexual partners.10
If you're diagnosed with herpes, tell your partners and ask the clinic for advice. Partners with symptoms should be checked. Testing for partners without symptoms is decided case by case.11
Do not reach for antibiotics before you know what's causing your symptoms. They will not clear herpes or thrush, and they can trigger thrush.
Frequently asked questions
Can thrush be mistaken for chlamydia?
Yes, it can. Both can cause unusual discharge and pain when you pee, so it’s easy to confuse them. The big difference is that chlamydia often has no symptoms at all, while thrush usually causes itching and soreness. Chlamydia needs antibiotics and thrush needs antifungal treatment, so a test is the best way to know which one you have.
Can you have chlamydia and thrush at the same time?
Yes. Having one infection doesn’t protect you from another, so it’s possible to have both at once. Antibiotic treatment for chlamydia can also trigger thrush in some people. If your symptoms don’t clear up after treatment, or new ones appear, speak to a GP, pharmacist or sexual health clinic.
Can you have thrush without symptoms?
The yeast that causes thrush, Candida, often lives in the vagina without causing any problems, and you don’t need treatment if you have no symptoms. Thrush itself usually causes itching, soreness or a thick, white discharge. If you’ve been diagnosed and your symptoms have cleared, there’s no need to treat again unless they come back.
Should my partner get treated too?
It depends on the infection. With chlamydia, your partner should be tested and treated, and you should not have sex until you’ve both finished treatment. With herpes, partners should go to a sexual health clinic if they get any symptoms, such as blisters or sores. With thrush, partners usually don’t need treatment unless they have symptoms themselves.
References
- UK Health Security Agency. Sexually transmitted infections and screening for chlamydia in England: 2024 report. GOV.UK; 2025. gov.uk
- NHS 111 Wales. Chlamydia. NHS 111 Wales; 2026. 111.wales.nhs.uk
- NHS. Genital herpes. NHS website; 2026. nhs.uk
- NHS Highland Sexual Health. Genital herpes. NHS Highland; 2026. nhshighlandsexualhealth.scot.nhs.uk
- NHS Lanarkshire. Genital herpes. NHS Lanarkshire; 2026. nhslanarkshire.scot.nhs.uk
- NHS. Can a man catch thrush from a female partner? NHS website; 2021. nhs.uk
- Sexual Health Sheffield. Thrush. Sheffield Teaching Hospitals NHS Foundation Trust; 2026. sexualhealthsheffield.nhs.uk
- NHS 111 Wales. Thrush in men and women. NHS 111 Wales; 2026. 111.wales.nhs.uk
- Government of Jersey. Thrush (candida infection). gov.je; 2026. gov.je
- NHS. Chlamydia. NHS website; 2026. nhs.uk
- Patel R, et al. 2024 British Association for Sexual Health and HIV (BASHH) UK national guideline for the management of anogenital herpes. BASHH; 2024. bashh.org
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.