Sexually transmitted infections: What parents need to be sure their teens know

A conceptual drawing of a kiss showing two young people from below the knees, one on tiptoes in untied red sneakers and cropped pants, one in black sneakers

It’s never easy for parents to talk to their teens about having sex. Many parents feel that talking about it is the same as condoning it, so they are hesitant to do so. But according to the most recent Youth Risk Behavior Survey (YRBS), a national survey of high school students, by the end of high school 30% have had sex.

It can be impossible to know for sure if your teen has had sex. Even if they haven’t, it’s likely that at some point they will — and they need to have information to help keep themselves safe and healthy.

What parents should know about sexually transmitted infections

Sexually transmitted infections, or STIs, are very common. They may be caused by bacteria, viruses, or other microorganisms, and spread through all kinds of sex. While most STIs are treatable, they can affect fertility in both women and men, can cause health problems for a baby during pregnancy, and can sometimes lead to lifelong infection or serious complications. That’s why teens need to know about them.

Below are the high-level facts about some of the most common infections: what causes them, what symptoms may occur, and how they are treated.


Chlamydia is the most frequently reported bacterial STI in the United States — but just as many cases are asymptomatic, so the numbers may be higher than we realize.

Symptoms, if they are present, can include discharge from the vagina or penis, pain with urination, or pain and swelling of the testicles (this is rare). A test of the urine (or a swab from the affected area) can diagnose it, and it is curable with antibiotics. If left untreated it can lead to infertility, more commonly in women than men.


Gonorrhea is another STI caused by a bacteria, and it can also be asymptomatic. When symptoms occur, they are very similar to chlamydia. Gonorrhea also can cause infertility in both women and men. While it is treatable, some infections have been resistant to the usual antibiotics used, so additional testing and treatment is sometimes needed.


Trichomoniasis is caused by a protozoa. It is another STI that can be asymptomatic. When there are symptoms, they are usually itch, irritation, and discharge. It is curable with medication.


Syphilis has been on the rise. In the first stage of infection there is usually a firm, round, painless sore where the infection entered the body. The sore is generally there for three to six weeks, but as it is painless it may go unnoticed.

In the second stage there is a more extensive rash, though it can be faint and go unnoticed, along with general feelings of illness such as fever, sore throat, fatigue, swollen lymph nodes, or weight loss.

If syphilis still goes unnoticed it can linger in the body for years, sometimes affecting organ systems, including the brain. It is curable with antibiotics, but if found late the damage it can do may be permanent. This infection can be very serious during pregnancy.


HSV (herpes simplex virus) causes blistering sores. There is both oral herpes (mouth sores) and genital herpes. Oral herpes, caused by HSV1, is not usually caused by sex — but it can lead to genital herpes through oral sex. Genital herpes is more commonly caused by HSV2.

The sores of herpes can recur throughout life. There is no cure for herpes, but there are medications that can shorten or prevent outbreaks. This infection can be particularly dangerous during pregnancy, although the risks can be managed with good prenatal care.


HPV (human papilloma virus) is the most common sexually transmitted infection. It can be transmitted even by close skin-to-skin touch, and infections are generally asymptomatic.

Most cases of HPV (90%) get better by themselves — but if they don’t, over time the virus can cause genital warts or certain cancers. Luckily, there is an effective vaccine to prevent HPV that can be given starting at age 9.


HIV (human immunodeficiency virus) is more common among people who have other STIs — mostly because having STIs is a sign of risky sexual behavior. It can be very hard to know if a person has it, because the early symptoms can feel like having the flu, and then people can move into a long period of time of having no symptoms at all.

While there is no cure for HIV, there are medications to control it, as well as medications that can prevent it.

Talking to teens about preventing STIs

All of this sounds scary. But there are actually some simple things teens can do to prevent infections or minimize complications, which is why parents need to talk with them.

Teens can:

  • Use condoms every single time they have sex — and use them properly. According to the report mentioned above, about half of sexually active high schoolers don’t use condoms regularly.
  • Limit their number of sexual partners — and have frank conversations with those partners before having sex. Asking about sexual history, and getting testing before starting a sexual relationship, can make a difference.
  • Get tested regularly. Sexually active teens should be tested for gonorrhea and chlamydia every year, or more frequently based on their sexual history or symptoms. Testing for other infections may be a good idea too. In the YRBS, 95% of high schoolers had not been tested for STIs in the past year, which is frightening given that nearly a third report being sexually active.

Make sure your teen sees their doctor regularly. And encourage them to be honest with their doctor during their visits. As a parent, you can help by giving your teen confidential time alone with the doctor.

About the Author

photo of Claire McCarthy, MD

Claire McCarthy, MD, Senior Faculty Editor, Harvard Health Publishing

Claire McCarthy, MD, is a primary care pediatrician at Boston Children’s Hospital, and an assistant professor of pediatrics at Harvard Medical School. In addition to being a senior faculty editor for Harvard Health Publishing, Dr. McCarthy … See Full Bio View all posts by Claire McCarthy, MD

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