What are sexually transmitted infections (STIs)?

Sexually transmitted infections, commonly called STIs, are diseases that are spread by having sex with someone who has an STI. These conditions are also known as sexually transmitted diseases (STDs). You can get an STI from sexual activity that involves the mouth, anus, vagina, or penis.

STIs are serious illnesses that require treatment. Some STIs, like HIV, cannot be cured and are deadly. By learning more about STIs, you can learn ways to protect yourself from these diseases. STIs include:

What are the symptoms of sexually transmitted infections (STIs)?

Sometimes, there are no symptoms. If symptoms are present, they may include:

  • Bumps, sores, or warts near the mouth, anus, penis, or vagina
  • Swelling or redness near the penis or vagina
  • Skin rash
  • Painful urination
  • Weight loss, loose stools, night sweats
  • Aches, pains, fever, and chills
  • Yellowing of the skin (jaundice)
  • Discharge from the penis or vagina (Vaginal discharge may smell bad.)
  • Bleeding from the vagina other than during a monthly period
  • Painful sex
  • Severe itching near the penis or vagina
  • Discharge from the penis
  • Discharge from the vagina that is different than usual (different odor, color, amount, or associated with irritation)

Last reviewed by a Cleveland Clinic medical professional on 04/14/2015.


  • Marrazzo JM, Holmes KK. Sexually Transmitted Infections: Overview and Clinical Approach. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e. New York, NY: McGraw-Hill; 2015. library.ccf.org Accessed 5/8/2015.
  • Centers for Disease Control and Prevention. Sexually Transmitted Diseases (STDs): Diseases & Related Conditions Accessed 5/8/2015.
  • Planned Parenthood Federation of America Inc. STDs Accessed 5/8/2015.
  • National Institute of Allergy and Infectious Diseases. Sexually Transmitted Diseases Accessed 5/8/2015.

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