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Sexually transmitted diseases, or sexually transmitted infections (STIs), usually pass from one person to another through sexual contact. Most are fairly common, and effective treatment is available, especially in the early stages.

Some STIs are benign, but others can lead to severe complications if a person does not seek treatment.

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

Anyone can contract an STI, regardless of their sexual orientation and hygiene standards. Many STIs can transmit through nonpenetrative sexual activity.

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

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Treatment is available for many common STIs.

Chlamydia results from an infection with Chlamydia trachomatis. It is a common infection that can spread through anal, vaginal, and oral sex. A pregnant woman can also transmit it to the baby during delivery.

Chlamydia does not usually produce symptoms, but it can result in infertility and other complications if a person does not receive 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 the infection occurs as a result of anal sex or if the infection spreads from another area. This can lead to:

  • rectal pain
  • rectal bleeding
  • rectal discharge

In those who do develop symptoms, these will usually appear 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 notice itching in the areas they affect.

The first stage in the life cycle will be the appearance of the eggs, which lasts 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 day or two, the females will lay more eggs, and the cycle will continue.

Pubic lice can spread from person to person 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 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, genitals, and some other parts of the body.

HSV-1 usually affects the mouth. People can contract it through saliva or if there is a herpes-related sore around their partner’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.

A person cannot contract herpes from 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, they can spread it 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 symptom is a blister around the mouth, anus, or genital area. These blisters can break, causing a painful sore that takes a week or longer to disappear.

Some symptoms of initial infection include:

  • fever
  • body aches
  • swollen lymph nodes

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

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

A person might never know that they have the herpes virus, but they can still transmit it 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:

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

A woman may pass this infection to the 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 offer 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 both males and females, 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 risk 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. Sexual contact is one way of transmitting HIV, but it can transmit in other ways, too.

HIV leaves a person more prone to certain other infections. People with HIV also have a higher risk of having 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 develop HIV.

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

Treatment can reduce the amount of the virus present within 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 the person cannot transmit HIV 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 during vaginal or anal penetrative sex
  • taking PrEP, which is a drug that can help prevent the development of HIV in people exposed 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 a vaccination to prevent it.

Many people experience no symptoms, but they can still pass on the virus to others.

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

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

HPV can spread through:

  • vaginal and anal sex
  • oral sex
  • genital-to-genital contact
  • from a pregnant woman to the fetus, 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 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 be 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 can help prevent the transmission of the virus. A person who has the virus should wash their hands carefully after touching an affected area of skin to prevent spreading the virus to another part of the body or another person.

Find out more here about molluscum contagiosum.

Scabies is a contagious skin condition caused by 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, symptoms may appear after 2–6 weeks. If they have scabies again, symptoms can appear 1–4 days after exposure. A person can transmit scabies before they know that they have it.

Transmission is usually through skin-to-skin contact and 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 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. It 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.

A person can pass on the bacterium at any point during the infection. Syphilis can also pass from a woman to the fetus 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 membrane, such as the mouth, vagina, or anus
  • swollen lymph nodes
  • hair loss
  • headaches
  • weight loss
  • muscle aches
  • fatigue
  • a 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 21 days after 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 caused by the bacterium Neisseria gonorrhoeae. It is highly contagious and, without treatment, can lead to life threatening complications.

A person can transmit gonorrhea during oral, vaginal, or anal sex. If they touch an infected area of the body and then touch their eye, gonorrhea can also lead to pink eye.

A pregnant woman can also pass the infection to the baby during delivery.

N. gonorrhoeae thrive in warm, moist parts of the body, such as the vagina, penis, mouth, rectum, and eye. A person can transmit this infection 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 a burning pain in the throat and swollen lymph nodes.

In females, the infection can lead to pelvic inflammatory disease. Males may experience an 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. 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 symptoms. If they do, these usually appear up to 10 days after exposure.

Find out more here about gonorrhea.

Chancroid is a rare bacterial infection caused by Haemophilus ducreyi. It causes painful sores on the genitals. The only way to transmit and contract it is through sexual contact.

Symptoms include a painful, genital ulcer. Chancroid can also increase the risk 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 of 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 they have had exposure to an STI, or if they have a sexual partner who has or may have an STI.

A doctor can test for STIs to confirm whether or not an infection is present.

Treatment for bacterial infections is with antibiotics. However, some STIs — such as gonorrhea — appear to be developing a resistance to 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 problem, and treatments are available that can either cure or help a person manage the infection. Seeking early treatment will also reduce the risk of complications.

A primary care doctor or a specialist clinic can help. For anonymous advice, people can call the national hotline (1-800-232-4636) 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 a person contract from oral sex? Find out here.

Using a condom or other barrier method can help prevent the spread of many STIs, though these 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 a new partner about safe sex and any past infections
  • both partners getting tested before starting a new sexual relationship
  • having vaccinations to protect against some infections
  • taking care when using alcohol or recreational drugs, as these can increase the chance of engaging in risky behavior

Various condoms and barrier contraceptives are available for purchase online.