15 Things You Should Never Keep in Your Car (and Why)

We've all been there. That quick dash to the grocery store that turns into an impromptu rendezvous with friends, or maybe you forget to take things out of the car and inadvertently become a target for thieves. Before you know it, the backseat looks like a storage unit — or worse, you find your car's window smashed because you left something in plain sight and now have to deal with a hefty bill to get it replaced.

While it's easy to say "I'll get [insert item] out of the car tomorrow," not everything is car-friendly. Here are 15 things you should never keep in your car — and the reasons might surprise you. 

Many medications have specific temperature storage guidelines to maintain their efficacy. Exposing them to excessive heat or cold can compromise the drug's active ingredients and render them useless or less effective. This means that they might not work when you need them — or, in some cases, could even produce harmful effects. 

When it comes to medications, the United States Pharmacopoeia (USP) advises storing them in a cool and dry place in temperatures that range from 59 to 86 degrees Fahrenheit. 

Our favorite gadgets — from smartphones and gaming consoles to laptops and cameras — typically contain lithium-ion batteries that do not fare well when exposed to extreme temperatures. Excessive heat can cause the batteries to malfunction or even explode, while the cold can drain battery life and damage LCD screens. Leaving valuable electronics in the car can also make it a tempting target for thieves.

Aerosol cans such as deodorants, hairspray, or cleaning products contain propellants that can expand when exposed to high temperatures, creating a dangerous or even life-threatening situation. This is due to the increased internal pressure that expands in heat and can lead to the can exploding. Believe it or not, your car can get extremely hot when parked in the sun, with temperatures sometimes soaring past 120 degrees.

Similarly, lighters contain pressurized flammable gas that can pose a fire hazard when exposed to high temperatures. Lighters — especially small, disposable ones — are also easily forgotten in glove compartments or door pockets and can burst or explode when their internal pressure become too high. 

Related: Ways You're Ruining Your Car and Don't Even Know It

This one should go without saying, but leaving anything of value such as your purse, wallet, cash, or important documents in the car can make you a target for pesky thieves. Even if you've stashed them away, seasoned criminals know the usual hiding spots like glove compartments and center consoles.

Losing essential items such as identification documents and credit cards can also make you a victim of identity fraud. Not to mention the hassle that comes with having to call and report theft or block the lost cards.

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Leaving food in the car — even if it's just for a few hours — can cause it to spoil and leave your car smelling like a fish market on a hot day. Warm, enclosed spaces are also perfect breeding grounds for bacteria like E.coli and Salmonella, which can lead to food poisoning if consumed. In particular, highly perishable foods such as raw meat and vegetables can easily spoil when left in high temperatures. 

Related: Why You Should (Almost) Never Defrost Meat in the Microwave

The plastic and acetate materials often used in eyewear can melt or become misshapen in high heat. Lenses — whether they're prescription or sunglasses — can also get damaged and affect their clarity and efficacy. In cold temperatures, these materials can become brittle, making them more prone to breakage. 

Related: Designer Sunglasses You Can Buy at Costco at a Discount

Cosmetics have an ideal storage temperature, and the temp of your car isn't it. Whether it's lipstick, foundation, or an eyeshadow palette, exposing these products to excessive temperatures can alter their texture, consistency, and color payoff. Lipsticks and liquid products can melt or separate, while cosmetics like blush and powdered foundation might turn crumbly or crack.

Also, fluctuating temperatures in your car can promote the growth of bacteria in makeup, leading to potential skin irritations and breakouts. 

When heated, certain plastics may release chemicals like bisphenol A (BPA) into the water that could have potential health implications when consumed. In addition, when exposed to sunlight, stagnant water in plastic bottles can become a breeding ground for bacteria, increasing the risk of ingesting microplastics and other harmful microorganisms that could jeopardize your health.

If you're a wine connoisseur, then you know that ideal temperature and humidity conditions are key to helping wine taste its best; stashing a bottle of wine in a sweltering car is far from ideal. Excessive heat can alter the wine's taste and may also cause the air inside the bottle to expand and force the cork out — leaving you with a mess and a nasty stain that will be tough, if not impossible, to remove. 

For spirits, high temperatures can cause evaporation, which may change the flavor and strength of the drink. 

Instruments — especially those made of wood — are sensitive to temperature and humidity changes. Since wood can warp or expand when exposed to high temperatures, stashing an instrument in the car (even in the trunk) can alter the material's quality and affect its sound or playability. 

Even with windows cracked open slightly, the temperature inside a parked car can quickly soar to dangerous conditions. The extreme heat can lead to heatstroke in humans and pets, which can be fatal. Similarly, in cold weather, cars can act as refrigerators by trapping in cold air, making them dangerously frigid.

When batteries are exposed to high temperatures, they can leak the acidic (or alkaline) liquid inside, which can damage electronic devices. In extreme cases, they can even burst — potentially causing an accident or fire hazard. The corrosive fluids leaking from batteries may also cause skin irritation, while the released chemicals may produce toxic fumes that can be hazardous to humans and pets when inhaled in an enclosed space such as a car.

Just like aerosol cans, canned beverages like sodas, beers, or sparkling waters are pressurized containers. When left in a car — especially during hot days — the liquid inside can heat up, causing the can to expand and potentially explode. Not only is this dangerous, but it can also leave you with a sticky, challenging mess to clean up.

Temperature changes can also alter the taste and carbonation of the drink. And is there anything more disappointing than popping open a can of soda and expecting a fizzy, satisfying sip, only to be met with a nasty, flat drink? 

When it comes to art supplies such as paints, pastels, and crayons, the car isn't their best storage spot. Art materials are sensitive to temperature changes: Oil paints can become more fluid in high heat, while crayons and pastels can melt or become brittle. Canvases and drawing papers can also warp or become discolored when exposed to heat or direct sunlight.