Treats such as preserved jams and jellies, cookies, cakes and personalized packages of candies make crafty (and economical) homemade holiday gifts. But if the gift-givers whipped up these and other goodies themselves, those delectables could be passing along botulism too, reports MSNBC.

Food-borne botulism is a paralyzing illness caused by botulinum spores. (These spores live on fresh food surfaces and die when exposed to air.) When food gets canned, the process produces a low oxygen environment where spores can linger and reproduce the harmful bacteria.

While botulism cases are rare in the United States (the CDC reported 18 cases in 2008), it’s still important to watch out for home-cooked goods that go bad. And although you can’t spot a nasty spore just by looking at canned foods, you can take steps to avoid getting sick from spoiled home-cooked eats.

First, be cautious about eating low-acidic homemade canned foods, such as green beans, carrots, vegetable salsa, chocolate sauces and pestos. The lack of acid in these foods allows spores to germinate, so home canning them in boiling water may not be enough to ensure they’re safe to eat. (In contrast, home-canned high-acid foods, such as fruits, tomatoes with added lemon juice, and pickled products with a certain amount of vinegar, are usually OK.)

Second, ask questions. If you receive a home-cooked food gift, ask when and how the giver made it and where he or she got the recipe. (Cooks should only use tested recipes found on the United States Department of Agriculture [USDA] website.) If you’re not happy with the gift-giver’s answer, toss the food.

Next, check the jar.  Food shouldn’t stick out of the liquid and be discolored or moldy. If you notice any of these unappetizing signs, then the food is probably not safe to eat.

Finally, if the food is canned, look for a vacuum seal. Why? Because the vacuum seal prevents contaminated air from getting back into the product. If this seal is missing, it’s a sure sign the food preparer used improper and unhealthy canning techniques.

Click here to learn which popular party foods are often the most contaminated.