A crispy and juicy apple can be a delightful snack.

Still, like other fruits and vegetables, apples only stay fresh for so long before they start to go bad.

In fact, apples that are far past their expiration date can eventually become unsafe to eat, making it important to know how to tell when they’re no longer fresh.

Although eating apples that are starting to age isn’t always dangerous, apples are subject to mold growth just like other fresh produce.

Mold is caused by microorganisms and may cause allergic or respiratory reactions in some people.

Some microorganisms grow mycotoxins, which are responsible for many foodborne illnesses.

Apples are subject to a mycotoxin called patulin, which is produced by the Penicillium expansum species.

When patulin is consumed in large amounts, it can cause nausea and bleeding ulcers and may even increase your risk of cancer.

Mycotoxins can also disrupt your gut bacteria, which may negatively affect your immune system and increase your risk of developing other illnesses.

It’s best to discard apples that show signs of expiration, as they carry the risk of toxic mold. Apples are especially at risk of growing mycotoxins like patulin, which can be dangerous to consume.