22 Things You Should Never Leave in Your Car

While it’s beneficial to keep your car stocked with essential items, some may pose a danger, attract thieves, or become damaged if left inside your vehicle. The interior of a vehicle can be a surprisingly hostile environment for a wide range of everyday objects, as well as for small children and pets.

Keep reading to get a comprehensive list of things you should never leave in your car.

Key Takeaways Children are especially vulnerable to heatstroke in parked cars because their bodies heat up much faster than adults, increasing the risk in hot weather. Similarly, you should avoid leaving pets, such as dogs, in the car because they can quickly overheat. Extreme temperatures can alter the chemical composition of medications, requiring careful storage in accordance with package instructions to ensure their effectiveness. Visible items like wallets or purses in cars attract thieves, posing risks of financial loss, identity theft and the cumbersome process of replacing personal documents. Essential documents are vulnerable to damage and theft in cars, with heat and humidity accelerating deterioration.

1. Children

While summer driving with the family, the temperature inside a car parked in the scorching sun can put your children at an increased risk of heatstroke if you leave them inside. Heatstroke occurs when the body's temperature rises to dangerous levels. Children's bodies heat up three to five times faster than adults, making them more susceptible to the effects of high temperatures.^[1]

As a result, you should always bring your children with you, even if you’re running a quick errand inside a store.

2. Pets

Like children, pets can quickly become overheated in a car, as the temperature inside can increase dramatically in just half an hour, even at relatively moderate outside temperatures.^[2] Dogs, in particular, are less efficient at cooling themselves than people, relying primarily on panting to regulate their body temperature.^[3]

3. Medications

Many medicines are sensitive to temperature fluctuations, and exposure to extreme heat or cold can alter their chemical composition.^[4] Refer to the storage instructions on your medication packaging and keep medicines in a controlled environment to ensure they remain safe and effective.

4. Wallet or Purse

Thieves often target vehicles for visible valuables, such as wallets or purses. These high-value targets can contain cash, credit cards, identification and personal information that thieves could utilize. For example, a thief could use the information inside a stolen wallet or purse to make unauthorized purchases, withdraw funds or even steal your identity, leading to long-term financial and legal complications.

The process of canceling cards, securing accounts and recovering from identity theft can be lengthy and stressful. Additionally, replacing personal documents such as your driver's license and Social Security card can be cumbersome and time-consuming.

5. Important Documents

Documents such as passports, birth certificates, legal papers and financial records contain sensitive information that, if stolen, can be used for identity theft and fraud. The interior of a car can also be an unfriendly environment for paper-based materials, where direct sunlight exposure and heat can cause fading and deterioration.

Outside of your proof of insurance card, it may be safest to leave important documents at home. However, if you are averse to leaving a physical copy of your proof of insurance in your car, many insurance companies allow you to access an electronic version through their mobile app. You can also keep a copy of your proof of insurance inside your wallet or purse, taking it with you when you leave your car.

6. Perishable Foods

Leaving perishable food in your car in hot weather can lead to spoilage, foodborne illness and waste. Foods like dairy products, meat, fish and prepared meals can quickly become unsafe to eat when exposed to temperatures above 40°F (4°C) for more than two hours, as bacterial growth accelerates in this temperature range.^[5] In warm weather, the temperature inside a car can rise rapidly in just a few minutes, dramatically increasing the risk of spoilage.^[2]

Consuming spoiled food can lead to food poisoning, with symptoms ranging from mild discomfort to severe health issues. Moreover, the odors from spoiled food can permeate your car's interior, creating unpleasant smells that are difficult to eliminate. So, get your groceries inside as soon as possible, and be sure to bring in those leftover nachos.

If you’re on a road trip, consider opting for drive-thrus and sit-down restaurants instead of perishables.

7. Certain Drinks

Leaving certain drinks in your car, especially for prolonged periods, can affect their quality and safety. Beverages like milk, juice and even some carbonated drinks can spoil or ferment when exposed to high temperatures, leading to unpleasant tastes and odors and potentially causing foodborne illness if consumed.

Wine can be particularly problematic, as heat can accelerate aging, causing it to "cook," which flattens its flavors and aromas, making it taste dull and lifeless. Similarly, cold temperatures can cause the liquid to freeze and expand, potentially pushing out the cork or cracking the bottle.

8. Water Bottles

When exposed to high temperatures, potentially harmful chemicals from plastic water bottles, such as bisphenol A (BPA), can leach into the water.^[6] Additionally, water bottles that have already been opened and left in the heat can grow bacteria.

9. Batteries

High temperatures can cause the chemicals inside batteries to expand, potentially leading to leakage of corrosive liquids that can damage electronic devices and car interiors. Cold temperatures, on the other hand, can reduce a battery's performance and lifespan by slowing the chemical reactions that power it.

Furthermore, battery leakage not only poses a risk to electronic devices but also represents a significant environmental hazard, as the chemicals can be harmful if they come into contact with the skin or are ingested. To mitigate these risks, store batteries in a temperature-controlled environment and avoid leaving them in your car for extended periods.

10. Lighters

If you leave a lighter in a hot car, you could expose yourself and your vehicle to dangerous situations because of the flammable liquids it contains. When exposed to high temperatures, the fluid inside a lighter can expand, increasing internal pressure. This can cause the lighter to leak flammable liquid or gas, posing a risk of fire or injury.

11. Electronics

Leaving electronics in your car, especially in extreme temperatures, can lead to irreversible damage.^[4] The internal components of electronic devices, such as smartphones, laptops and tablets, are sensitive to temperature changes. Exposure to high heat can shorten the lifespan of these components, and battery parts can even melt together or warp. Conversely, cold temperatures can freeze the liquid crystal displays (LCDs) and reduce battery life.

12. Luggage

Luggage often contains valuables such as clothing, personal items, electronics and sometimes travel documents or cash, which are attractive to thieves looking for an easy score. A break-in can result in the loss not only of expensive items but also of irreplaceable personal belongings and sensitive information. Furthermore, the absence of these items can significantly disrupt travel plans, leading to additional expenses and complications, especially if travel documents are required.

13. Jewelry

Visible jewelry left in your car can attract the eye of thieves, leading to the loss of valuable and often sentimental items. To prevent theft, keep your jewelry on your person or leave it at home, not in your car.

14. Cosmetics

High temperatures can cause makeup products like lipsticks, foundations and creams to melt, altering their texture and making them difficult or impossible to apply. Even products that do not visibly melt may undergo chemical changes that affect their color, consistency and effectiveness.

Extreme cold can cause the moisture in certain cosmetics to expand. Once the expansion reaches a certain point, it can cause a break in the container and lead to leaks inside your car.

15. Plants

Since the interior of a car can quickly become an oven in the sun, plants are vulnerable to wilting or even burning if left inside for long enough.^[2] Conversely, cold temperatures can freeze plants’ cells, causing damage that can be equally fatal. Furthermore, a lack of air circulation in a parked car can increase humidity, which can encourage mold or fungus growth.

16. Aerosol Cans

Leaving aerosol cans in your hot car can be extremely dangerous due to the pressurized contents. As temperatures rise, the pressure inside the aerosol can increase, potentially leading to an explosion.^[7] Even if the can does not explode, the increased pressure can cause the canister to leak, releasing potentially harmful chemicals into the car's interior.

17. Low Gas Tank

Driving or leaving your car with a low gas tank, especially in colder weather, can lead to several issues beyond the risk of running out of fuel. In cold temperatures, condensation can form in an empty or nearly empty gas tank.

This water can then mix with gasoline and, if it reaches the fuel lines, may freeze, potentially blocking fuel flow to the engine and causing starting issues or even engine damage.

Furthermore, consistently running on a low fuel tank can cause the fuel pump to overheat and wear out prematurely, as the fuel acts as a coolant for the pump. Debris at the bottom of the tank can also be drawn into the fuel system, causing clogs and inefficiencies.

18. Sunscreen

It is bad to leave sunscreen in the car because prolonged exposure to heat can encourage bacterial and fungal growth. Heat breaks down preservatives, leading to the proliferation of these microbes. Heat can also degrade the active ingredients in chemical sunscreens, reducing their effectiveness and exposing you to harmful UV rays.^[8]

Additionally, leaving spray sunscreen in the car can be even worse because the pressurized container is sensitive to high temperatures, which may increase the risk of leakage or explosion.

19. Art Supplies

Storing art supplies in your car can lead to their deterioration and potential safety hazards, depending on the materials involved. Items like oil paints, spray paints and certain solvents are susceptible to temperature changes. High heat can cause these materials to expand, potentially leading to leaks or, in the case of spray paint, even explosions. Cold temperatures, on the other hand, can cause some liquids to freeze, leading to separation and rendering them unusable.

20. Musical Instruments

Musical instruments are often sensitive to temperature and humidity changes, and extreme heat can warp wood, melt glue and damage finishes, while cold temperatures can cause cracking and misalignment. For example, the delicate components of string instruments, such as violins and guitars, are particularly susceptible to warping and neck bending.

21. Glasses

Extreme heat can warp or melt the frames of glasses, especially if they are made of plastic, and can cause the lenses to become distorted. In the case of sunglasses, prolonged exposure to heat can also damage the UV protective coating, reducing their effectiveness in protecting your eyes from harmful UV rays. Similarly, cold temperatures can make certain materials brittle, leading to cracks or breaks, especially in older or more delicate frames.

22. Firearms

Leaving a firearm in your car can make you a target for thieves, as the number of car break-ins that resulted in a gun theft rose from 5% to 9% between 2018 and 2022 and was the primary source of gun thefts during that time. About half of the reported stolen guns from cars occurred when parked at residences. Additionally, gun thefts from cars parked in accessible parking lots and garages increased by 76% over the same time period.^[9]

Safety Tips for Storing Items in Your Car

Below are a few safety tips to keep in mind when storing items in your car:

• When leaving your car in a publicly accessible area, ensure you lock all of your car’s doors, close all windows, turn the car off and take the keys with you, even if you’re only briefly running inside somewhere. Car thefts can occur in just a few seconds, so it is critical to take precautions even when away from your vehicle for a short time.^[10]
• If you have a valuable item that you aren’t actively transporting, it’s probably best to leave it at home and not bring it in the car. If you need to bring valuables, keep them out of sight or in a secure area, such as a locked trunk.
• Hide your valuables before reaching your destination. If you’re parking in a public area, a thief may be scoping out potential targets, so you might make yourself more appealing to thieves if you wait to move valuables until you arrive at your destination.
• Park in areas that are well lit and have lots of people, such as a populated side street or busy parking garage.
• Avoid leaving personal documents and identification, such as your driver’s license or the vehicle’s title, in the car. You should consider keeping your car insurance information in your purse or wallet, taking it with you when you leave.
• Ensure your car’s alarms and anti-theft features are working properly.