Why
Plain cereals like cornflakes aren't toxic, but they're full of sugar and refined carbs with no benefit for pets. Chocolate cereals contain cocoa, and fruit cereals may include raisins, both of which are dangerous. Some contain nuts or xylitol, so always check the label. Served with milk, the lactose can cause diarrhea.
How to give it / if eaten
Don't give it as a treat. A few plain flakes just need watching. If your pet ate a chocolate cereal or one with raisins or macadamias, grab the box and call your vet right away.
Watch for these signs
Large amounts can cause vomiting, diarrhea or bloating. With chocolate cereal, watch for hyperactivity, a racing heart or tremors; with raisins, vomiting, lethargy and reduced urination.
FAQ
My dog ate a bowl of chocolate cereal.
It has less cocoa than chocolate, but it can still be risky depending on the amount and your dog's weight. Check the box and call your vet right away.
Can I give cereal with milk?
Many pets get diarrhea from the lactose in milk, and cereal is sugary. Neither makes a good treat.
General information only. Weight, age and health conditions change how a pet reacts, so ask your vet if you are worried.