Horse owners become concerned about poisoning from oak trees in the fall when the acorns are so thick on the ground. Hence the commonly used term of acorn poisoning. However, this is not the only toxic part of the plant. Horses are susceptible to oak poisoning caused by the tannic acid that accumulates in new leaves, buds, and acorns. Though rarely a problem in horses there are circumstances that can make poisoning more likely. This article addresses causes, clinical signs, diagnosis, treatment, and prevention of oak toxicity.

There are many species of oak which differ in many primary characteristics including native locations. Oaks vary from small to large trees. The leaves are alternate, simple, toothed or lobed, dark green and glossy leaves that become red to brown in the fall. The fruit is a nut (acorn) with a woody cap.