Whether you’re trying to save money or be less wasteful in general, shopping at secondhand stores, garage sales, and flea markets is a good strategy. Not only do you get to save an item from the landfill, but you can usually pay a fraction of the retail cost.

Of course, some items work better than others when it comes to a second life. Used gym equipment, tables, and dishes make great secondhand buys, for example. Not only can you clean them up easily, but a quick wash can leave them in “like new” condition. Likewise, used clothing can also be an excellent value. After paying pennies on the dollar for your new shirt or skirt, all you need to is throw it in the washer.

10 Items You Shouldn’t Buy Secondhand

But some items aren’t meant to be bought, used, and resold. Sometimes there’s a safety issue or hazard, other times it’s the unknown that poses the greatest risk. Here are 10 items you should never buy used unless you understand the risks:

Baby Cribs

After multiple baby and toddler deaths, the Consumer Product Safety Commission banned drop side cribs in 2011. Meanwhile, many other crib bans and safety recalls have taken place due to hazards such as lead paint, strangulation, or other dangers. If you’re unsure of whether a used crib has been recalled, you can conduct some research on your own at CPSC.gov.

Car Seats

Although used car seats can be bought for pennies on the dollar, that doesn’t always make them a good value. Not only do car seats have an expiration date or “shelf life” you should pay attention to, but there is often no way to know if a car seat has been damaged or compromised.

The fact that safety technology improves every year is another reason to just buy new if you’re in doubt. If you do choose to buy used, you should at least buy from someone you know who can verify that seat has never been involved in an accident.

Mattresses

Good mattresses are very expensive, so buying one used might seem like a good deal, but it rarely is. Although you’ll save a bundle upfront, a used mattress will almost always have bodily fluids, dust mites, and pounds of dead skin embedded deep in the fabric. Even worse, a mattress infested with bed bugs could easily cost you thousands of dollars in extermination fees. The Environmental Protection Agency lists some telltale signs you can list for when checking for bed bugs, but they certainly aren’t foolproof.

Makeup

While it’s generally okay to buy unopened makeup from an individual, you should never buy makeup that has been used in any capacity. Why? Because used makeup harbors all kinds of bacteria that you don’t want near your ears, eyes, and mouth. Yuck.

Vacuum Cleaners

Have you ever heard of someone unloading a vacuum that still works great? Yeah, me neither. Most people sell their vacuums and get a new one when their old one stops doing its job. Plus, you never know what that vacuum was used for, and how many dust mites and bacteria are lurking inside. If you’re looking to save money on a vacuum cleaner, try a factory refurbished or reconditioned model or check the scratch-and-dent section.

Shoes

Although it might be fine to purchase lightly worn used footwear, experts warn against buying used shoes that have been worn on a regular basis. Since shoes mold to their owner’s feet, a heavily used pair could cause you pain or even health problems over time.

Baby Bottles

While “newer” used bottles might be fine after you sanitize them, experts caution against stocking up on bottles that are more than a few years old. Why? Because many older bottles contain BPA – a chemical that was banned for use in baby bottles by the FDA in 2012. If you’re unsure whether a used bottle is BPA-free, you’re better off buying new.

Worn Cookware

While sturdy pots and pans may be an exception, you should never buy a piece of cookware with a flaky or worn non-stick coating. The chemicals contained in non-stick coatings such as Teflon can leech out into your food while you’re cooking. In other words, the savings you earn by buying used cookware might come with a side of unsavory chemicals and potential carcinogens.

Upholstered Furniture

Similar to used mattresses, used furniture is often home to dust mites, bacteria, and even bed bugs. And since you can’t throw a used sofa in the washer, you may never get it 100% clean. The bottom line: Only buy upholstered furniture from someone whose cleanliness you trust – not from strangers!

Hats

Although used hats can cost pennies on the dollar compared to new, that doesn’t make them a good bargain. The fact is, used hats may have never been washed – and may even be impossible to wash. Therefore, a used hat will usually contain someone’s hair, dead skin, and sweat — not to mention the potential for head lice. Ewww.

If you’re shopping secondhand to save, you’re definitely on the right track. Still, there are times when buying used presents a huge hazard or risk that makes the savings a moot point. The next time you’re shopping for a secondhand item, ask yourself these questions:

Will this item fit in my washer?

Can I clean and sanitize this item thoroughly?

Can I verify its history?

Do I know this item is safe?

If you answer “no” to any of these questions, you’re probably better off sucking it up and buying new. Because sometimes, the savings just aren’t worth it.

What items would you add to the list? What items do you refuse to buy secondhand?