Sexually transmitted infections (STIs) usually pass from one person to another through sexual contact. Examples include chlamydia, crabs, and genital herpes. Treatment can depend on the type of STI.

HIV has other routes of transmission. For example, this STI can spread through the use of unsterilized drug needles as well as sexual contact.

STIs can affect anyone, regardless of the individual’s sexual orientation or hygiene standards. Many STIs can spread through nonpenetrative sexual activity.

This article looks at some common STIs, how to prevent them, and when to seek help.

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Chlamydia results from an infection with Chlamydia trachomatis. It is a common infection that can spread through anal, vaginal, and oral sex. It can also spread to a baby during childbirth.

Chlamydia does not usually cause any symptoms, but it can result in infertility and other complications if a person does not seek treatment for it. It is easy to cure with early treatment.

If symptoms do occur, they may include a change in vaginal discharge and burning pain during urination.

Chlamydia can also affect the rectum if it occurs as a result of anal sex or spreads from another area of the body. This can lead to:

  • rectal pain
  • rectal bleeding
  • rectal discharge

In those who do develop symptoms, they will usually appear around 7–21 days after exposure.

Learn more about chlamydia here.

Crabs, or pubic lice, usually attach to pubic hair. Sometimes, however, they can affect the hair in the armpits, mustache, beard, eyelashes, or eyebrows. They are very small and difficult to see, but a person will likely notice itching in the areas they affect.

The first stage in the life cycle will be the appearance of the eggs. This stage lasts for around 6–10 days. After hatching, the lice will look like tiny crabs. They need blood to survive and will live for around 2–3 weeks. In the last couple of days, the females will lay more eggs, and the cycle will continue.

Pubic lice can spread during close physical contact, including sexual contact. They can also transmit via shared towels or bed linen. However, they cannot spread via toilet seats.

To remove pubic lice in the genital area, a person can apply a 1% permethrin solution or a similar product. These are available over the counter from most drugstores and pharmacies. It is essential to follow the instructions precisely.

If pubic lice are affecting the hair near the eyes, the person may need a prescription medication.

Learn more about pubic lice here.

The herpes simplex virus (HSV) is a common virus that affects the skin, cervix, and genitals, as well as some other parts of the body.

HSV-1 usually affects the mouth. It can spread through saliva or if there is a herpes-related sore around another person’s mouth. It can pass to the genital area during oral sex.

HSV-2 can affect the genital area, the anal area, and the mouth. It transmits through vaginal, oral, and anal sex.

Herpes cannot spread via utensils, toilet seats, swimming pools, soaps, or bedding. However, if a person touches a body part where herpes is present and then touches another part of their body, the herpes can spread to that area.

Once herpes is present, it stays in the body. It usually remains dormant, however, and many people will never develop symptoms.

The main symptoms are blisters around the mouth, anus, or genital area. These blisters can break, causing a painful sore that takes a week or longer to heal.

Some symptoms of initial infection include:

  • fever
  • body aches
  • swollen lymph nodes

Some people never have symptoms, some have only an initial outbreak, and some have repeated outbreaks.

The first bout is usually the most severe, but people with compromised immune systems — due, for example, to HIV — have a higher risk of experiencing severe symptoms overall. Having herpes can also increase the chance of contracting or transmitting HIV.

A person might never know that they have the herpes virus, but it can still spread to others.

There is currently no cure, but medication can help relieve any symptoms. Daily antiviral medications can help prevent the spread of herpes.

Wearing a condom will not completely prevent the transmission of herpes.

Learn more about herpes here.

Hepatitis B can cause a long-term infection and result in liver damage. Once a person has the virus, it can remain in their semen, blood, and other bodily fluids.

Transmission is possible through:

  • engaging in sexual contact
  • using nonsterile equipment for injections
  • puncturing the skin with a sharp object where the virus is present

This infection can pass to a baby during pregnancy or delivery. However, a doctor can advise on ways to prevent this.

As long as the nipples are not cracked, the risk of transmitting the virus through breast milk is negligible, according to the Centers for Disease Control and Prevention (CDC).

People at high risk of contracting hepatitis B should ask their doctor about a vaccine, which can offer some protection. The vaccine may not provide long-term immunity, however, and the person may need booster doses for continued protection.

Learn more about hepatitis B here.

Trichomoniasis, or trich, can affect anyone, but females are more likely to experience symptoms. Trichomonas vaginalis is the cause of this infection.

In females, it is most likely to affect the vagina. In males, the infection can develop in the urethra.

Transmission can occur through penetrative sex and vulva-to-vulva contact.

Many people do not experience any symptoms. If symptoms do occur, they may include:

  • unusual discharge
  • pain during urination
  • pain during ejaculation
  • pain or discomfort during sex

Trich can also lead to pregnancy complications and increase the chance of both contracting and transmitting HIV.

A doctor can prescribe medications to resolve trich, but both partners will likely need treatment, or the infection may return. Without treatment, trich can last for months or years.

Learn more about trichomoniasis here.

HIV is a virus that attacks the immune system. It can spread through sexual contact and some other means.

HIV makes a person more prone to certain other infections. People with HIV also have a higher risk of contracting other STIs. Without treatment, this susceptibility to infection worsens and may lead to life threatening complications.

Once a person has HIV, the virus will be present in their bodily fluids, including semen, blood, breast milk, and vaginal and rectal fluids. If these fluids enter another person’s body, that person can also contract HIV.

This can happen through sexual contact, sharing needles, contact with broken skin, giving birth, and breastfeeding.

Treatment can reduce the amount of the virus present in the body to an undetectable level. This means that the amount of the virus within the blood is so small that blood tests cannot detect it. It also means that it cannot spread to other people.

A person with undetectable HIV must continue to follow their treatment plan exactly as the doctor prescribes to keep virus levels low.

Some other ways to prevent transmission include:

  • using a condom or other barrier method of contraception during vaginal or anal sex
  • taking preexposure prophylaxis, which is a drug that can help prevent HIV in people with exposure to the virus
  • not sharing needles
  • using gloves and disposing of sharps carefully, such as when working in a healthcare setting

Learn more about HIV here.

Human papillomavirus (HPV) refers to a group of viruses that affect the skin and mucous membranes, such as the throat, cervix, anus, and mouth. There are various types, and some pose a higher risk than others.

HPV is common. It affects around 79 million people in the United States. Nearly everyone who is sexually active will have HPV at some point in their lives, unless they have received a vaccination to prevent it.

Many people experience no symptoms, but in these cases, it is still possible for the virus to spread.

Some types of HPV can lead to genital warts. These tend to be low risk.

Having HPV can also increase the risk of cervical cancer and throat cancer.

HPV can spread through:

  • vaginal and anal sex
  • oral sex
  • genital-to-genital contact
  • from a pregnant person to a baby, though this is rare

Vaccination can help prevent the transmission of HPV.

Learn more about HPV here.

Molluscum contagiosum is a contagious viral skin infection that is usually benign.

It can affect both adults and children. Doctors consider it an STI when it occurs in adults but not when it occurs in young children. Experts believe that it is a type of pox.

Among adults, transmission tends to occur through skin-to-skin contact or lesions, usually during sexual activity.

Symptoms include small, round bumps and indents on the skin. There may only be one of these. The bump or bumps usually disappear without treatment, but this can take time, and they remain contagious while present.

Some ways of removing the bumps include taking certain prescription medications, applying chemicals or an electrical current, or freezing them.

Using a barrier method of contraception can help prevent the transmission of the virus. Anyone who has the virus should wash their hands carefully after touching an affected area of skin to prevent the spread of the virus to another part of the body or another person.

Learn more about molluscum contagiosum here.

Scabies is a contagious skin condition that develops due to Sarcoptes scabiei, which is a mite. This condition can cause a pimple-like rash to appear anywhere on the body.

The first time a person has scabies, the symptoms may appear after 2–6 weeks of exposure. If they have scabies again, symptoms can appear 1–4 days after exposure. Scabies can spread before a person even knows that they have it.

Transmission usually occurs through skin-to-skin contact and due to sharing items such as towels and bedding.

A doctor can prescribe topical creams that kill the mites. While a person has scabies, they should avoid skin-to-skin contact with others. Once it has cleared up, they should decontaminate any personal items, including all bedding and clothes.

Learn more about scabies here.

Syphilis stems from an infection with the bacterium Treponema pallidum. It is a potentially serious infection, and early treatment is necessary to prevent permanent damage and long-term complications.

There are usually four stages. In the first stage, a person may notice a round, firm sore at the site of the infection, usually around the genitals, anus, rectum, or mouth. This tends to last for 3–6 weeks.

The sore may not be visible, since it is often painless and may be hidden, for example, in the vagina.

The bacterium can spread at any point during the infection. Syphilis can also pass to a baby during pregnancy.

At the secondary stage, there may be:

  • a non-itchy rash of rough, brownish or red spots on the palms of the hands or soles of the feet
  • lesions in the mucous membranes, such as the mouth, vagina, or anus
  • swollen lymph nodes
  • hair loss
  • headaches
  • weight loss
  • muscle aches
  • fatigue
  • fever

In the latent stage, the symptoms disappear, but the bacteria remain in the body and can continue to cause damage.

In the tertiary stage, life threatening complications can affect the brain, nervous system, eyes, heart, and several other organs. Symptoms at this stage will depend on which part of the body the syphilis affects.

The only way to confirm whether or not syphilis is present is by conducting a test. If the result is positive, the person should inform their sexual partner or partners, and they, too, should seek medical advice.

Symptoms will appear around 21 days after the transmission of the bacteria, on average, but they can take between 10 and 90 days to appear.

Learn more about syphilis here.

Gonorrhea is a common infection that develops due to the bacterium Neisseria gonorrhoeae. It is highly contagious and, without treatment, can lead to life threatening complications.

Gonorrhea can spread during oral, vaginal, or anal sex. If a person touches an infected area of the body and then touches their eye, gonorrhea can also lead to pink eye.

This infection can also spread to a baby during childbirth.

N. gonorrhoeae thrive in warm, moist parts of the body, such as the vagina, penis, mouth, rectum, and eye. This infection can spread during sexual contact.

There are often no symptoms, but if they do occur, they may include:

  • pain during urination
  • discharge
  • swelling of the genitals
  • bleeding between periods

If it affects the rectum, it can lead to:

  • anal itching
  • pain during bowel movements
  • discharge

An infection that occurs as a result of oral sex can lead to burning pain in the throat and swollen lymph nodes.

In females, the infection can lead to pelvic inflammatory disease. Males, meanwhile, may experience inflammation of the epididymis, which is the tube that stores sperm. Both conditions can affect fertility.

As soon as a person has gonorrhea, the bacteria can spread to other people and to other parts of the body through physical contact. Receiving treatment with antibiotics can usually resolve the infection.

Symptoms can appear 1–14 days after infection. Males usually notice symptoms 2–5 days after exposure. Females often do not experience any symptoms at all, but if they do, the symptoms will usually appear up to 10 days after exposure.

Learn more about gonorrhea here.

Chancroid is a rare bacterial infection that develops due to Haemophilus ducreyi. It can only spread through sexual contact.

It causes painful sores on the genitals. Chancroid can also increase the chance of HIV, and it can make HIV harder to treat.

Treatment is with antibiotics. Anyone who receives a diagnosis of chancroid should inform any partners they have had sexual contact with within the past 10 days.

Learn more about the symptoms and treatments associated with chancroid here.

Many STIs will not cause symptoms, so a person should not wait until symptoms appear before seeing a doctor.

Instead, people should seek medical advice if they think that they have had exposure to an STI.

A doctor can test for STIs to confirm whether or not an infection is present. They will then prescribe the most appropriate treatment option.

The sections below will look at some treatments and tips for coping with an STI.

Antibiotic treatment

Treatment for bacterial infections is with antibiotics. However, some STIs — such as gonorrhea — appear to be developing a resistance to the antibiotics that doctors commonly prescribe to treat them.

It is essential to complete any type of antibiotic treatment, even if the symptoms disappear. Stopping treatment early may allow remaining bacteria to grow again, and symptoms may return. At this stage, the infection can become harder to treat.


Vaccines can help protect a person from HPV and hepatitis B. People can discuss their situation with a healthcare provider, who will advise about vaccinations.

Dealing with stigma

Many people find it hard to talk about STIs due to concerns about stigma. However, STIs are a common health concern, and treatments are available that can either cure the infection or help a person manage it. Seeking early treatment will also reduce the risk of complications.

A primary care doctor or a specialist clinic can help. For anonymous advice, a person can call the national hotline (800-232-4636) or visit this website. Help is available in both English and Spanish.

Home testing kits for various STIs are also available for purchase online, though a person should seek confirmation of the result from a doctor.

Which STIs can spread through oral sex? Find out here.

Using a condom, dental dam, or other barrier method of contraception can help prevent the spread of many STIs, though this will not prevent the transmission of infections that spread as a result of skin-to-skin contact.

Some other ways to reduce the risk of transmitting or contracting an STI include:

  • talking to any new partners about protected sex and any past infections
  • ensuring that both partners undergo testing before starting a new sexual relationship
  • receiving vaccinations to protect against some infections
  • taking care when using alcohol or recreational drugs, as these can increase the chance of risky sexual behaviors