Guinea pigs are sensitive animals, and feeding them the wrong foods can lead to severe health issues. It's essential to know what foods are toxic to guinea pigs. Some common toxic foods include chocolate, onions, garlic, potatoes, and avocado. These items are harmful and can cause serious illness or even death. In addition to these toxic foods for guinea pigs, avoid using processed foods, as they can upset their digestive system. Foods toxic to guinea pigs also include iceberg lettuce and rhubarb, which can lead to diarrhea or poisoning. Remember that bad foods for guinea pigs aren't always obvious, so stick to safe options like hay, fresh vegetables, and fruits in moderation to keep your furry friend healthy.