TamponsHeat can make tampons go bad before their expiration date, and it can be really hard to tell a good tampon from a bad one. And yes, tampons do expire, usually after five years from production. Even though most tampons aren't going to sit on a shelf for five years, if you use them at all, you should know they don't last forever. Worse still is that excessive moisture can make a tampon moldy way before its expiration date. Who keeps track of the humidity inside their car? Air, it's worth remembering, tends to be more humid in higher temperatures. That's not exactly how it works, we know, but it's true in essence.Besides, that's not the point. The point is: Don't leave tampons in a hot car. That said, it almost certainly takes more than one or two days in a hot car to ruin an unopened pack of tampons. If you're worried about the bag you forgot in the car earlier this week, don't. If you've been doing this for a while, we have some bad news. Mold can spread through a tampon from the inside out, making it nearly impossible to tell if one has already been affected. If you're unsure if a tampon is safe and it has been stored improperly for a while, throw it out. The risk is not worth it.All kinds of contraceptionYes. Really. Heat can ruin every kind of contraception. Condoms, which are probably quite high in the list of items people purposefully leave inside their cars, are made of plastic -– latex, most of the time –- so of course they're vulnerable to heat. Sources indicate 104°F as the maximum heat condoms can endure for just a few days, and 86°F as the optimum long-term storage temperature. Cars can get much, much warmer than that, potentially ruining the effectiveness of contraceptives in less than a week.What about birth control pills, or a contraceptive ring? Chances are, there are far fewer cars full of pills than condoms, but they're equally susceptible to heat. Actually, pills and rings are even more sensitive. As with almost all medicine, they should be discarded if they're stored at a high enough temperature (sometimes as low as 68°F) for a few days or longer. Not only can their effectiveness be compromised, but they might make you sick as well. Thankfully, there's a simple solution to this problem — don't leave contraceptives inside your car when it's really hot.