Is there a difference between venomous and poisonous?

Eastern diamondback rattlesnakes are one of six venomous snakes in North Carolina. They use venom for capturing prey and self-defense.
(Photo by Dr. Craig Harms)

May 2005

Yes, and we’re so glad you asked!

Although the terms are often used interchangeably, they have very different meanings. Both pertain to poison, but the distinguishing factor is the method of delivery.

A toxin that is harmful when absorbed or eaten (ingested) is considered poisonous. Many plants, amphibians and mushrooms are poisonous. For example, we know to stay clear of poison ivy because a brush with the plant can result in a nasty rash. Amphibians are another good example. Have you ever seen your dog play with a frog and end up with a foamy mouth? That’s because the dog ingested a mild poison from the frog’s glands. The frog uses the poison as a defense against predators.

Venomous, on the other hand, is a toxin that can cause harm when injected. Injections can be delivered by barbs, stingers, spurs, spines, tentacles and other defense mechanisms. Examples are  jellyfish,  stingrays wasps and bees.

A number of animals are venomous, with snakes being the first to come to mind. It’s interesting to note, however, that no snake species have ever been known to be poisonous, nor do they have toxin-producing glands on their skin that could be absorbed or ingested to cause harm. Six species of snakes in North Carolina are venomous. They must bite in order to deliver venom to their victims.