Before I went to college, I received two pieces of unsolicited advice from an older, more experienced relative: (1) Always shave your legs, because you never know what's going to happen, and (2) you'll probably be fine if you try cocaine a couple of times.

I really wish that family member had talked to me about UTIs instead.

Urinary tract infections are the second most common kind of infections in humans after respiratory infections. And they're particularly rampant among young people with vaginas. UTIs afflict vagina-havers at a rate eight times that of penis-havers. An estimated one in three people with vaginas will have to receive antibiotics to destroy the monsters raging in their urethras by age 24. And if you don't know what's happening to you, UTIs can mess a person up pretty badly. Left untreated, a UTI could spread to the bladder or the kidneys, or even to the bloodstream, at which point an untreated UTI could become life-threatening.

What's more, UTIs have a high rate of recurrence. One study published in the American Journal of Public Health in 1990 found that 26.6 percent of women who contracted a UTI got another within six months. And 95 percent of recurring UTIs occur when the same organism that was treated by antibiotics grows back two weeks later. UTIs cost the United States $3.5 billion a year in missed work and health-care costs.

But here's why I really want you to care about UTIs: The bacteria that young people deal with today are not your grandparents' bacteria. A growing number of bacteria found in urethras are antibiotic resistant—"probably at least 10 percent," according to science journalist Maryn McKenna. Some researchers have traced these drug-resistant bacteria back to cheap supermarket chicken or turkey. A culprit could be the antibiotics fed to livestock to help them grow in massive industrial and disease-vulnerable pens. Plus, UTIs become more likely as you get older and have more sex.

What is a UTI?

Oftentimes, the bacteria present in a UTI can be traced back to your gut. The most common, E. coli, lives in your lower intestine. Sometimes what lives in your lower intestine can make its way out your butt and into your urethra. (This is also why wiping front-to-back is generally a good idea.) Uropathogenic E. coli can attach to cells in your urethra and produce substances that break down those cells. That's how E. coli can colonize your urethra and possibly migrate up to the bladder or the kidneys.

How do I know if I have a UTI?

Classic UTI symptoms: a burning sensation, frequent urge to pee, cloudy pee, bloody pee, cramping, fatigue, chills.

How do I prevent UTIs?

PEE AFTER SEX! That is one of the most effective things you can do. To repeat: PEE AFTER! Other stuff: Drink lots of water, don't have contests with yourself to see how long you can "hold it in," wipe from front to back, and don't douche or use weird sprays down there. The vulva and vagina are self-regulating body parts. And get prescribed antibiotics—because that's what you will need. Don't allow your bacteria to become resistant.

Does cranberry juice work?

Studies haven't concluded that cranberry juice helps, but the Mayo Clinic recommends it anyway. Cranberry supplements—which are less sugary than chugging a gallon of that stuff they sell at Walgreens—can't hurt you, at least.

Anything else I should know?

If you've gotten a urinary tract infection before and know what it's like, trust yourself. Vagina-havers are pretty good at knowing their own bodies. A 2001 study found that 84 percent of women who self-diagnosed with UTIs were spot-on. If you drink a ton of water before going to the doctor, you may flush out too much of the bacteria—enough to throw off the results of a urine culture test. So the best bet is to go to the doctor the minute you think you have a UTI. Don't hesitate. And good luck out there. Remember: PEE AFTER SEX!