It depends on the sexually transmitted infection (STI) you have. Symptoms may appear within a few days or weeks, but sometimes they don't appear until months or even years later. The main exception to that “3 to 10 day” period is herpes. In some cases, ulcer outbreaks can come and go at regular intervals for the rest of a person's life.
There is no cure for herpes, but there are medications that can reduce the frequency and intensity of outbreaks and also reduce the chances that you'll transmit herpes to your partner. Because HIV is incurable, medications have been developed that prolong life and reduce symptoms, so once the initial symptoms go away, you shouldn't experience any more symptoms of STDs. According to the Centers for Disease Control and Prevention (CDC), skin rashes, fever, swollen lymph nodes and pain in the testicles are considered secondary symptoms of common STDs, such as syphilis or gonorrhea. The only way to make sure you don't have an STD after an unprotected sexual encounter is to get tested, Ghanem says.
It's very unlikely that you'll experience STD symptoms the day after engaging in sexual activity. Symptoms of an STD may appear the next day, but this depends largely on the sexually transmitted disease you've been exposed to, as well as the severity of the symptoms your sexual partner is experiencing. What's more, “common symptoms of STDs, such as bumps around the pubic area or discharge from the genitals, can be confused with other problems, such as ingrown hair, pimples or yeast infections. Your Sexual Health offers a wide range of STD tests that can be done at the clinic or at home to help give you peace of mind knowing if you have been infected with an STD.
As you can see, the time frame in which symptoms of an STD will occur is different for each type of STD. STDs can be prevented from spreading infection through body fluids by using birth control methods, such as a condom, but this is not a 100% reliable method of using STDs. If you're currently concerned about your sexual health or that of another person, a home STD test can identify common sexually transmitted infections. You could also be at greater risk of serious complications, from arthritis to cancer, if your STD isn't treated.