Horse chestnuts contain esculin, which is a type of poison. These nuts may lead to death when consumed in raw form, according to the National Institutes of Health.
The Food and Drug Administration considers the whole horse chestnut to be an unsafe herb. Consuming the nuts or drinking a tea made from horse chestnut leaves can lead to horse chestnut poisoning. Such toxicity can lead to death, although individuals are more likely to experience side effects such as salivation, nausea, vomiting, diarrhea, headaches, convulsions, a breakdown of red blood cells along with circulatory and respiratory failure. When properly prepared, horse chestnut products are safe to consume. This process generally involves standardized extract formulations to remove esculin, the most toxic component.