|Warning: That's not guinea pig food! Stay away! (source: André Karwath/Wikipedia)|
However, unlike other pets, rodents like guinea pigs are unable to vomit, even if they eat something toxic, which could make poinsettias somewhat more of a risk for us than for other pets. Fortunately, the worst thing that typically happens if we eat a poinsettia is an upset stomach. If your guinea pig eats a poinsettia, make sure they are still eating and drinking, and otherwise behaving normally. Call your vet if you notice any behavior changes.
Of course, the best thing to do to keep toxic plants away from us, whether they're mildly toxic or very toxic.