4

You Can "Catch" Cancer

Organ transplants come with well-documented medical risks, like infection, rejection, or turning their new owner into a murderous psychopath. There's also a small chance they can transmit cancer.

Sometimes this is the result of a misdiagnosis. In 2008, doctors transplanted organs from a man they thought died of bacterial meningitis. It turned out to be lymphoma, which was passed on to three recipients, two of whom died as a result. Oops.

More often, the signs of disease aren't visible. Doctors may get as few as six hours to prep and screen a donor before their organs go bad, because organs apparently have the shelf lives of avocados. By the time a thorough autopsy is performed, the tumors are already snuggled up in a throw blanket and binging Netflix in some poor new schmuck's chest cavity. There have also been freak occurrences, including the curious case of an operating surgeon who suffered a cut, which later developed a wee bit of cancer thanks to hitchhiking tumor cells.

3

Cavities Are Contagious

You can brush and floss all you like, but huckin' a makeout with a sketchy bar rat just once could still ruin your oral health -- and we're not talking about herpes (though yes, you will also get herpes). According to one dentist, a 40-year-old patient who had never had a cavity in her life suddenly showed up to her biannual cleaning with two, plus some bonus gum disease. The diagnosis? A gross-ass boyfriend. It would seem the lady's new gentleman hadn't seen a dentist in 18 years. He must have had a great personality.

It's not limited to mouth-wrestling partners, either. The bacteria that cause gum disease and cavities, like Streptococcus mutans and Streptococcus sobrinus, can be passed from one person to another as easily as a cold. Parents most often pass these bacteria when they shares utensils or food with their children, or blow on a steaming stack of Minion-shaped pancakes. These bacteria then kick their shoes off and colonize junior's mouth, causing problems even later in life when permanent teeth arrive. It's just one more thing you can blame on your mom.

2

OCD And Tourette's Are Not Purely Mental

No, you're not going to catch obsessive-compulsive disorder from a public soap dispenser, but there is a more roundabout way in which an otherwise psychologically healthy person might wind up suffering from it. It was first suggested that OCD (as well as Tourette syndrome) could be transmitted to children in 1998, but the phenomenon wasn't officially recognized by the National Institute of Mental Health until 2012. The group of disorders is known as pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection, or PANDAS. Good ol' National Institute of Mental Health, hiding horror behind cute animals since The Secret Of NIMH.

PANDAS involves sudden onset of symptoms of OCD or Tourette syndrome immediately (or sometimes several months) after a child suffers a streptococcal infection. Even when the strep throat subsides, the bacteria can still be hiding in the body under the guise of totally healthy cells. When the immune system eventually wises up and sends antibodies, they attack the basal ganglia, the brain region in control of things like fine motor movements and behaviors. As a result, affected children develop tics or obsessive-compulsive routines, including constant repetition of mundane tasks such as hand-washing. It affects about 1 in 200 children, and can usually be reversed with antibiotic use if detected in time. So this is one scenario in which it's totally permissible to freak the hell out about your kid's sore throat.

1

Sexually Transmitted Food Poisoning

You've probably never heard of it, but ciguatera fish poisoning is the world's most reported marine toxin disease -- even more common than Long John Silver's Syndrome. You can catch it from eating fish full of toxic algae ... or, bizarrely, sexual intercourse. With a person, that is, not a fish.

Cacophony/Wikimedia CommonsWell yeah, probably also with a fish, but we imagine that if you're committed to boning a sturgeon, you know the risks already.

That's what happened to two couples who were enjoying a Bahamian vacation together. After dinner one night, the men's legs began tingling, their perceptions of hot and cold reversed, and violent diarrhea ensued. Impressively, they didn't let an expensive seafood dinner go to waste and still managed to seal the deal, so to speak. As a result, their wives were rewarded with several weeks of burning pelvic pain of their own after the toxin was transmitted through their husbands' semen.

This horrific fate that can also cause miscarriages in pregnant women, hallucinations, and the unshakable impression that your teeth are falling out. Want to avoid it? Best of luck! Any fish that's eaten toxin-laced algae can cause ciguatera, so there's no way to tell which, if not all, of Red Lobster's dinner entrees will poison you. However, bigger fish like snapper are more likely to sicken you, so go small. On the bright side, the symptoms usually go away after a few days, but if you're terribly unlucky, it could last weeks. So, you know, try not to piss off any sea witches.

Support your favorite Cracked writers with a visit to our Contribution Page. Please and thank you.

For more, check out 4 Things Too Gross To Put In Pregnancy Books:

Follow us on Facebook. Because we love you.