Key points
- A sexually transmitted infection (STI) is an infection spread between people during sex or close sexual contact.
- STIs are common in teenagers and young adults who are sexually active.
- Using condoms or other barrier protection is the best way to avoid STIs.
- Your teen may not have symptoms if they have an STI.
- If your teen is sexually active, they should get tested for STIs regularly.
- STIs can have serious and harmful long-term health effects if untreated.
What is a sexually transmitted infection (STI)?
A sexually transmitted infection (STI) is an infection spread from one person to another during sex or close sexual contact. All types of sex and sexual activity with intimate body parts can pass on STIs – not just penetrative sex.
Anyone sexually active is at risk of STIs, including teens.
The risk of STIs is higher for teens who:
- have sex without using a condom or another barrier protection
- have multiple sexual partners
- start having sex with a new partner.
The best way to avoid STIs is to use barrier protection like condoms. Other forms of contraception, like the pill, do not protect against STIs;
they only prevent pregnancy.
Most common STIs in teens
Chlamydia
Chlamydia is the most common STI in young people. It is a bacterial infection caused by a bacterium called Chlamydia trachomatis that can infect the cervix, urethra, anus, throat, and sometimes eyes. Chlamydia is easy to treat with a short course
of antibiotics. Without treatment, chlamydia can lead to long-term problems like chronic pain and fertility issues.
Symptoms
Many people with chlamydia do not have any symptoms. That is why teens need regular STI checks if they are sexually active.
Teens with symptoms may have:
- discharge from the penis, vagina or anus
- pain in the pelvis or lower abdomen
- a stinging or burning feeling when peeing
- pain during sex
- vaginal bleeding after sex.
Gonorrhoea
Gonorrhoea is an infection caused by the bacterium Neisseria gonorrhoeae. It lives in the genital fluid of infected people, spreading through penetrative sex, shared sex toys and genital skin contact. Gonorrhoea can infect the cervix, urethra,
anus, throat and eyes. Sometimes, it spreads through the body, causing fevers and joint infections. Gonorrhoea is treatable with antibiotics.
Symptoms
People with gonorrhoea often do not have any symptoms.
Teens with symptoms may have:
- discharge from the penis, vagina or anus
- pain in the penis, vagina or anus
- a stinging or burning feeling when peeing
- pain during sex
- bleeding after sex
- pain in the pelvis or lower abdomen
- a sore throat.
How can my teen stay safe from STIs?
The best way for your teen to avoid STIs is by using barrier protection every time they are sexually active. External condoms are the most popular barrier protection for sex with a penis, but there are also:
- internal condoms
- dental dams (a thin, square sheet placed over flatter areas like the vagina and anus during oral sex).
If your teen is sexually active, you should encourage them to see their doctor regularly for STI checks. For most people, it is best to get tested every six to 12 months. It is very important that your teen takes any treatments their doctor prescribes.
Some STIs can spread through contact with other bodily fluids, like blood. Teach your teen to be cautious when doing anything involving these fluids, like getting tattoos, piercings or injections. If you know your teen is going to be doing one of these
things, encourage them to check that the equipment is sterile and all needles are new.
HPV vaccine
Human papillomavirus (HPV) is a virus spread by skin-to-skin contact. It can cause genital warts and cancers. Thankfully, there is a vaccine that can prevent most types of HPV. Teenagers in Australia can get the HPV vaccine for free at school in year
seven as part of the National Immunisation Program. Your teen does not need to be sexually active to get the vaccine.
If your teen missed the HPV vaccine at school or you moved to Australia from another country, it is not too late to protect them from the virus. Doctor’s clinics and some pharmacies will give your teen the HPV vaccine for free up to age 25 – they may
just charge a small admin fee.
Testing for STIs
Different kinds of tests check for STIs in both teens and adults. Testing may include:
- Swabs: A swab collects a sample of cells to test for STIs. If your teen does not have any symptoms, they can usually take the swab sample themselves. Their doctor or other health professional will explain how to do this. If your teen does have
symptoms, their doctor will take the swab sample.
- Urine tests: A urine (pee) test can also check for common STIs like chlamydia and gonorrhoea – especially if your teen cannot do a swab test.
- Blood tests: A blood test can check for certain STIs that a urine test or swab will not find, like HIV and syphilis.
What should my teen do if they think they have an STI?
If your teen may have an STI, they should:
- see their doctor as soon as possible
- stop having sex until they have seen their doctor.
Many major cities in Australia have sexual health clinics where teens can see a trained health professional without an appointment. They do not usually need to be a regular patient.
If your teen is diagnosed with an STI, their doctor (or other health professional) will:
- prescribe any treatments they need, like antibiotics.
- advise on how long to wait before they can safely have sex again.
- organise a follow-up test to make sure the treatment worked (if required).
- suggest ways to tell their sexual partner(s) they have an STI so the partners can get tested, too. This process is called 'contact tracing.' It is a critical step in stopping the spread of STIs.
Many STIs are 'notifiable infections'. This means the Australian Government Department of Health collects statistics on how many cases of these STIs there are every year. Doctors must tell the Department of Health every time a patient tests positive for
some STIs. They do not share full names or other personal information.
Common questions about STIs
Are cold sores a type of STI?
The virus that causes cold sores is in the same family as the genital herpes virus, also known as Herpes Simplex Virus (HSV). It spreads through kissing, sex, and genital skin contact. Some people do not get any symptoms with HSV, but others may
have painful blisters, ulcers or sores, pain and swelling in the genital area, and a rash or small cracks in the skin. Herpes is very common. There is no cure, so if your teen catches it, they will carry it for their whole life. However, people
with herpes can manage their symptoms with medicines and still live normal lives. Symptoms come and go; your teen may get cold sores when they are sick, tired or have low immunity. There are treatments to improve symptoms and stop them from
returning, but the virus will still be in the body.
Is a urinary tract infection (UTI) an STI?
A urinary tract infection (UTI) is not an STI, but sex can increase the risk of developing a UTI. This is because bacteria cause a UTI,
and sex introduces different kinds of bacteria to the genital area. Some symptoms of a UTI are the same as many STIs, too, like a burning feeling while peeing.
Should I be worried about my teen catching HIV?
Some people are at higher risk of HIV, such as men who have sex with men. If your teen fits in this category, it is a good idea for them to speak with a doctor or another health professional before they have sex. This is because there are other
ways they can protect themselves from the disease, including medicines like PrEP and PEP. These can help prevent HIV
before or immediately after being exposed to the virus.
Does my teen have to tell me if they have an STI?
Teenagers have a right to private and confidential health care. This privacy means they do
not usually need to tell you if they have an STI. However, a doctor may speak with you about your teen's care if they are not safe, such as if they are under 16 years old and have had sex with someone more than two years older.
For more information
Developed by The Royal Children’s Hospital (RCH) Adolescent Medicine department, with input from the Gynaecology and Infectious Diseases departments. We acknowledge the input of RCH consumers and carers.
Reviewed August 2025
Please always seek the most recent advice from a registered and practising clinician.