One of the most noticeable changes that may prompt concern is the appearance of bumps, blisters, ulcers, or sores. These can occur on or around the genitals, anus, lips, or other areas of skin that have had contact with an infection.
Several STIs can cause lesions, but their appearance varies considerably.
Genital herpes may cause clusters of small blisters that break open and form painful sores. Some people experience tingling, itching, or burning before the lesions appear. Others have symptoms so mild that they mistake them for an ordinary skin irritation, an ingrown hair, or a small cut. Herpes can also be transmitted when no obvious sore is present.
Syphilis may initially cause a sore called a chancre at the site where the infection entered the body. It is often firm and painless, which means it can go unnoticed, particularly when it develops in an area that is difficult to see. The sore may disappear without treatment, but the infection can remain and progress to later stages.
HPV can cause genital warts, which may appear as small, raised growths or groups of bumps. Their size and appearance vary. Some are barely noticeable, and many HPV infections cause no visible warts at all.
Yet bumps and sores are not exclusive to STIs. Folliculitis, ingrown hairs, contact dermatitis, friction, cysts, and other skin conditions can create similar-looking changes. Molluscum contagiosum, another viral skin infection, can also cause small raised bumps and may spread through close skin contact.
The important point is not to identify a specific infection by comparing a lesion with an online photograph. If you develop a new genital sore, unexplained blister, persistent growth, or unusual skin change after sexual contact, arrange a medical assessment. Avoid squeezing the area or applying harsh products, which can cause additional irritation.
If possible, seek care while a fresh sore or blister is still present. A clinician may be able to collect a sample to help identify its cause. Do not wait for the lesion to become painful before seeking advice.
2. Unusual Discharge or a Change in Odor
A change in genital discharge can sometimes be a sign of infection, particularly when it is accompanied by pain, irritation, or discomfort during urination. However, discharge naturally varies from person to person and may change throughout the menstrual cycle. A change in appearance does not automatically mean an STI is present.
In people with a vagina, chlamydia and gonorrhea may cause unusual discharge, bleeding between periods, or bleeding after sex. Trichomoniasis can cause genital irritation and a change in discharge, sometimes accompanied by an unusual odor. Many people with these infections, however, notice no symptoms at all.
In people with a penis, gonorrhea and chlamydia may cause discharge from the urethra. The discharge can vary in color and consistency. Some people also experience burning when urinating or discomfort around the testicles.
It is important not to use the color or smell of discharge as a self-diagnostic test. Bacterial vaginosis, yeast infections, urinary tract infections, and other non-STI conditions can cause overlapping symptoms. Some conditions may occur at the same time, making the picture more complicated.
If discharge changes persist, are unusual for you, or occur with pain, sores, bleeding, or a possible sexual exposure, seek medical advice. A clinician can recommend the appropriate tests and treatment. Avoid taking leftover antibiotics or using another person's medication, since the wrong treatment may fail to address the cause and can contribute to antibiotic resistance.
3. Burning or Pain During Urination
Pain, stinging, or burning when urinating is another symptom that deserves attention. It can occur when an infection irritates the urethra, the tube that carries urine out of the body.