What Are STDs? Symptoms, Causes, Testing & Treatment

STDs and STIs Explained: Causes, Symptoms, and Treatment

Sexual health can feel like an uncomfortable topic to bring up, even with a doctor. But understanding sexually transmitted diseases (STDs) — also known as sexually transmitted infections (STIs) — is one of the simplest ways to protect yourself and the people you care about. Below, the team at PULSE Clinic answers the questions people ask most, in plain language, so you know exactly what to look out for and what to do next.

What Are Sexually Transmitted Diseases (STDs)?

Sexually transmitted diseases (STDs), or sexually transmitted infections (STIs), are infections passed from one person to another through sexual contact. This is usually vaginal, oral, or anal sex, but some infections can also spread through other close physical contact. Herpes and HPV (human papillomavirus), for example, can spread through skin-to-skin contact alone, without full intercourse taking place.

What Causes STDs?

STDs can be caused by several different types of organisms, including:

• Bacteria (e.g., chlamydia, gonorrhea, syphilis)
• Viruses (e.g., herpes, HIV, HPV)
• Fungi
• Protozoa
• Parasites

Because the cause varies so widely, the right treatment depends entirely on correctly identifying which infection you have.

What Are the Most Common STDs?

Some of the most frequently diagnosed STDs include:

• Non-gonococcal urethritis (NGU) — including chlamydia, ureaplasma, and mycoplasma infections
• Chlamydia
• Gonorrhea
• Syphilis
• Herpes simplex (genital herpes)
• Genital warts (HPV)
• HIV/AIDS

What Are the Common Symptoms and Signs of STDs?

STDs and STIs can present in many different ways. Common symptoms include:

• Discharge from the urethra or vagina
• Dysuria (pain or burning when urinating)
• Genital sores or ulcers (which may or may not be painful)
• Blisters on the genitals
• Growths on the genitals
• Swollen lymph glands in the groin
• Rash on the genitals or elsewhere on the body

It's also possible for an infection to cause no symptoms at all. This is known as an asymptomatic infection, and it's more common than most people realise.

Do These Symptoms Always Mean I Have an STD?

Not necessarily. Rashes and growths on the genitals can have causes that have nothing to do with sexual contact, and not every case of discharge or dysuria is caused by an STI. Because so many conditions can look similar on the surface, it's important to see a doctor for an accurate diagnosis rather than guessing or self-treating.

How Long Does It Take for STD Symptoms to Appear?

The time between infection and the appearance of symptoms — called the incubation period — varies significantly by infection:

• Gonorrhea, non-gonococcal urethritis (NGU), and genital herpes: typically 2 days to 3 weeks
• Syphilis: typically 2 weeks up to several months
• HIV: can take several years for symptoms to appear, though it can be detected by testing much sooner

What Should I Do If I Think I Have an STD?

See a doctor as soon as possible. Avoid sexual contact in the meantime, since you could unknowingly pass the infection to someone else. Most importantly, do not self-medicate — incorrect or incomplete treatment can mask symptoms without actually curing the infection, and it can contribute to antibiotic resistance.

How Soon Should I See a Doctor After Sex With a New or Unfamiliar Partner?

See a doctor promptly if you notice any signs or symptoms of an STI. Even if you don't have any symptoms, testing may still be recommended after a potential exposure because some infections can take time to become detectable. Your doctor can advise you on the appropriate timing and types of tests, including HIV and syphilis testing, based on when the exposure occurred and your individual circumstances. Until you have received appropriate medical advice and testing, consider avoiding sexual contact or using condoms to reduce the risk of passing an infection to others. Avoid self-medicating with antibiotics, as the wrong treatment may be ineffective and can contribute to antibiotic resistance and other complications.

What Happens If an STD Is Left Untreated?

In some cases, symptoms may fade on their own — but this does not mean the infection is gone. Even without visible symptoms, the infection can remain active, continue spreading to other parts of the body, and eventually damage internal organs. Some of this damage can be permanent. This is exactly why early diagnosis and treatment matter so much.

Can Someone Have an STI Without Any Symptoms?

Yes, absolutely. Many STIs can cause no noticeable symptoms, making them difficult to detect without testing. Around 50% of men with chlamydia may have no symptoms, while approximately 10%–40% of men with gonorrhoea may experience an asymptomatic infection, depending on the site of infection and the population studied. Infections in the throat or rectum can be particularly difficult to recognise because they may cause few or no symptoms. Even when an STI is symptomless, it can still be passed on to sexual partners, which is why regular testing is important.

Are All STIs Curable?

Bacterial STIs are curable when treated early — this includes chlamydia, gonorrhoea, and syphilis. Most viral STIs, such as herpes, HPV, and HIV, are not curable, though they can often be effectively managed with treatment. Early treatment of any STI reduces the risk of passing it on and helps prevent long-term complications.

Can All STIs Be Diagnosed With a Blood Test?

No. Blood tests are only useful for diagnosing a limited number of STIs — mainly syphilis, hepatitis B, and HIV/AIDS. For most other STIs, doctors need to examine samples of discharge or swabs from the skin or mucous membranes to confirm a diagnosis.

What Is PCR31 STI Testing?

PCR31 is a molecular STI screening test that can detect genetic material from up to 31 different microorganisms in a single test. It can help identify infections such as chlamydia, gonorrhoea, mycoplasma, and herpes, including some infections that may cause few or no symptoms. Depending on your symptoms, sexual exposure, and the areas that may have been exposed, a doctor can advise whether PCR31 or other STI tests are appropriate.

One test. 31 microbes. Multiple body areas.

PCR31 Test - STD Screening Promotion at PULSE Clinic Thailand

• Prices are in Thai baht.
• Online results will be available at the PULSE Online Portal (POP) and the E-Doc mobile application
• For same-day result testing, the sample must be taken at the clinic before noon (12:30 PM)
• Same-day and next-day results are only available at the Bangkok, Pattaya, and Phuket branches

Contact us at info.bkk@pulse-clinic.com or chat on your preferred platform:

How Are STIs Treated?

Treatment depends on what's causing the infection:

• Bacterial infections are treated with antibiotics
• Viral infections are treated with antiviral medications
• Parasitic infections are treated with antiparasitic medications

There is no single medication that treats every STI, which is why correctly identifying the infection before starting treatment is so important.

Can You Be Immunised Against STIs?

Vaccines are available for two major STIs: hepatitis B and HPV (human papillomavirus). Aside from hepatitis B, having and recovering from an STI does not make you immune — you can be reinfected even after successful treatment, so ongoing prevention and safe practices remain important.

Key Takeaways

• STDs/STIs spread through sexual contact and, in some cases, skin-to-skin contact
• Symptoms vary widely, and many infections cause no symptoms at all
• Bacterial STIs are curable with early treatment; most viral STIs are manageable but not curable
• Never self-medicate — see a doctor for proper testing and diagnosis
• Vaccines exist for hepatitis B and HPV, but not for most other STIs

If you're sexually active, especially with new or multiple partners, regular testing is one of the most effective things you can do to protect your health and your partners' health — regardless of whether you have symptoms. The team at PULSE Clinic is here to help with confidential testing, diagnosis, and treatment.

Book Assessment and Treatment with us

Contact us at info.bkk@pulse-clinic.com or chat on your preferred platform:

Find PULSE Clinic Near You for STD Screening