Rajal C. Patel, MD, a gynecologist at the Northwestern Medicine Center for Sexual Medicine and Menopause, answers the most common questions about STIs and shares ways to protect yourself.

How common are STIs?

According to the Centers for Disease Control and Prevention (CDC), one in five people in the United States have an STI. Many people have no symptoms or are unaware that their symptoms are the result of an STI. Someone may be infected and not know it. People who are post-menopausal are at a higher risk, since vaginal tissue is thinner and more likely to tear during intercourse, making it easier for the infection to get into the bloodstream. If you are sexually active, it is important to practice safe sex even if preventing pregnancy is not the goal.

What is safe sex?

There is no such thing as 100% safe sex, because any sexual activity or intimate contact (not just intercourse) can result in an STI. However, condoms make sex safer. They can be purchased over the counter and online.

Condoms are the only method of birth control that also helps prevent STIs.

Types of condoms

External condom

• The external condom fits on the penis and can prevent infections that can affect the skin of the penis or in the semen.
• This type of condom can't protect against certain STIs like human papillomavirus (HPV) or herpes simplex virus (HSV) if those viruses are on the skin around external genital areas, such as the scrotum, vulva or upper thighs.
• External condoms come in different sizes.

Internal condom

• The internal condom fits inside the vagina or anus and is non-latex.
• The internal condom is intended for use in the vagina. It covers the cervix and vaginal walls, but also shields the vulva (the genital skin outside the vagina).
• For anal sex, the internal condom covers part of the inside of the anus, so there is less skin-to-skin contact, which also helps prevent STIs.
• No special fitting is needed because each condom will adjust to fit your body.

To reduce the transmission of STIs during oral sex, you can use a dental dam. A dental dam is a thin square sheet made with latex or polyurethane and is used as a barrier between the mouth and vagina or the mouth and anus. Similar to condoms, dental dams can be purchased over the counter and online.

How quickly after unprotected sex can symptoms of an STI occur?

Each STI has its own set of unique symptoms — or no symptoms at all. If you think you've been exposed, ask your primary care physician or advanced practice provider (APP) to test you. Tell your physician or APP about any symptoms you are having, such as:

• New skin sores
• Abnormal bleeding or discharge
• Pain with urination or pelvic pain

Your symptoms can help determine the type of screening needed.

Are STIs curable?

If treated, some STIs like gonorrhea, syphilis, chlamydia and trichomoniasis are curable. Other infections such as HSV, HPV, human immunodeficiency virus (HIV) and hepatitis B cannot be cured, but they can be managed with medication.

Is the only way to get an STI through vaginal, anal or oral sex?

Most STIs are spread through sexual intercourse and bodily fluid, but there are some infections that can be spread through close skin-to-skin contact. The STIs that have the highest risk of transmitting through skin-to-skin contact are:

• HSV
• HPV
• Syphilis
• Pubic lice
• Scabies

Do I need to see a special kind of physician if I think I have an STI?

No, but it is important that you are being evaluated by a healthcare professional who is an expert in the prevention, detection and treatment of STIs. Your primary care physician or APP is a great place to start.

Should I get tested even if I don't have any symptoms?

If you are sexually active, STI screening and timely treatment, if needed, are critical to protect your health and prevent transmission to others. Talk to your physician about STI testing at your annual exam or any time you have a new sexual partner or unusual symptoms to see which tests may be right for you. Testing is not a standard part of your annual exam, so your physician may not bring it up.

You can also view the CDC's STI screening recommendations.

How does STI testing work?

Depending on the type of STI, your physician may not need to do a physical exam, but will test your urine or blood. If you are symptomatic, a more thorough exam may be necessary.

Should I get the HPV vaccine?