1. The surface of onion is moldy and can't be eaten if peeled off.

2. After the onion is moldy, it will produce corresponding mycotoxins. These mycotoxins not only stay in the moldy position visible to the naked eye, but also may gradually spread to the part where no hyphae are produced. However, the spread of other parts does not reach the moldy amount, but there is still a risk of harm to health after eating. Therefore, for the sake of safety, it is best to throw away moldy things, whether onions or other foods, as soon as possible to avoid eating by mistake.