Buying secondhand products on sites like eBay or at yard sales can be a great way to save some money, but there are certain things you just should never buy in a 'used' state. Here are some examples.

Mattresses

Think about it. People have been sleeping on this thing, possibly for years. You don't want to take that into your home and use it yourself. There could be bed bugs, bacteria and who knows what else in that thing. Not to mention the fact that mattresses lose their springiness and strength over time.

Photo by Greg Ruffing

Helmets

Helmets only work to protect you when they're undamaged. If a helmet has been involved in a crash of some kind and suffered a dent or crack, it has lost a lot of its potential for keeping your head safe. Plus, new helmets and safety laws are being developed all the time, so older models might not even be legal or recommended anymore.

Car seats

Just like helmets, car seats can become totally useless if they've been damaged in the past. They have expiration dates and newer models will always be better equipped to keep your kids safe.

Cribs

When it comes to your kids, you need to spend the extra money to keep them safe and comfortable. Used cribs might be damaged or have missing parts that could turn them into deathtraps. It's not safe to buy this sort of thing secondhand.

Food processors

Food processors contain dangerous blades spinning around at high speeds. If they're faulty, there's no telling what sort of damage they could cause. Many products like this are actually recalled due to faults and problems, so don't buy them used.

Laptops

You really have no idea if a used computer is going to work. Not only could the previous owner have bashed it around over the years, they might damaged internal components or downloaded dangerous viruses onto the hard drive. You're much better off buying one from a proper retailer and getting a warranty.

Fluffy toys

These are just gross and should never be bought secondhand. There's no telling where a fluffy toy has been and what has happened to in the past. Kids aren't known for their hygiene and these things can be covered in lice, bacteria and more! Avoid them.