Both the acorns and leaves from oak trees can be poisonous to both children and adults when eaten in large quantities, according to Healthy Child Care. While acorns provide a great deal of nourishment for squirrels and other wild animals, excessive human consumption can lead to kidney damage with symptoms appearing anywhere from a few days to a few weeks after eating acorns.
In addition to the acorns' toxic nature, the small nut also poses a significant choking risk for small children, according to K-State Research and Extension. Because the acorn nut is exceedingly difficult to crack and even more time consuming to prepare for consumption, choking on the nuts, slipping on or being injured by the cracked, sharp shells of acorns and cleaning up the nuts before they seed are typically greater causes for concern with oak trees.
Acorns have high levels of tannins, which is the element in the nut that is poisonous, according to K-State Research and Extension. Useful for clarifying wine and beer, tanning leather and lending tea its astringency, tannin, a phenolic compound, when present in large quantities is a corrosive and poisonous acid. Acorn poisoning most often occurs in animals such as dogs and cattle, while acorns provide food for rabbits, voles, foxes, mice, raccoons, turkeys and woodpeckers.