Last week I caught a few minutes of the TV show Kourtney & Khloe Take Miami. The younger Kardashian sister was yelling at the older (now pregnant) one for being a “make-out whore.” She said something along the lines of: “You make out with so many people you’re going to get herpes. I’d rather you be having sex using a condom. At least then you’d be protected.”

It’s true that protected sex is much safer than unprotected sex. But you can still get sexually transmitted diseases even when you’re protected, and it will always be safer to be a “make-out whore” than it is to have protected sex with a lot of guys. The fact that condoms aren’t always a guarantee against STDs is just one thing you may not know about your sexual health. Here are some surprising and sobering truths:

1. You can still get an STD when using a condom

Always wrap it up. Using a condom is going to make you much less likely to contract an STD. But condoms aren’t perfect protection. Here’s the thing: STDs are spread two ways, through infected skin and infected fluids. Some STDs--like syphilis, herpes and HPV (human papillomavirus) -- can cause sores anywhere on the thighs, anus, scrotum, and butt. That means there’s plenty of potentially infected skin that isn’t covered by a condom. So while it’s very important to use a condom, don’t think that using one every time means you’ve eliminated your risk of getting an STD.

2. STDS aren’t always obvious

You can’t assume that if a guy isn’t walking around frantically scratching his crotch, he doesn’t have an STD. You also can’t assume that he’s clean just because his penis may look normal (and isn’t covered in barnacle-like bumps like some pictures you may have seen). Most people who have an STD don’t have any signs or symptoms. Others have symptoms that are so mild they either overlook them, or mistake them for a tiny cut or ingrown hair. So just because a guy may think he has no STDs, it doesn’t actually mean he’s clean. (And the same goes for you.)