Why it's dangerous
The plant contains saponins and polyphenolic compounds, with the highest concentration found in the nuts, causing gastrointestinal irritation in small animals and severe neurological and respiratory distress in large animals.
Toxic compound: Saponins and polyphenolic compounds
Good to know
Fagus sylvatica (European variety) is significantly more toxic than Fagus grandiflora (North American variety). While small animals usually only experience GI upset, grazing animals can face lethal consequences.
Sources
This page is informational and is not veterinary advice. If your pet has been exposed to something risky, contact your vet or an animal poison control line right away.