Dogs are not typically allergic to poison ivy. Some dogs, however, can develop a variety of symptoms in response to contact with the plant. In severe cases, they may require the attention of a veterinarian.
Poison ivy belongs to a group of plants known as toxicodendron radicans. Its toxic principle consists of a resinous oil found in the plant's sap known as urushiol.
Dogs typically get in contact with poison ivy when they walk or run in wooded areas and their fur brushes against the plant. In most cases the fur acts as a barrier, keeping the urushiol from touching the skin. In some cases, inquisitive dogs may ingest some parts of the plant.
While reactions are unlikely, they can occur. Dogs with sparse fur, whose skin is exposed to poison ivy, may develop irritated red patches, itchiness and bumps or swellings on the skin. If the plant was ingested, the dog may develop stomach upset characterized by vomiting and diarrhea.
Owners suspecting their dog has come in contact with poison ivy should avoid touching or petting their dog. The urushiol may easily transfer from the dog's fur to the owner's skin.
According to Petplace.com, owners should wear gloves and bathe their dogs for about ten minutes followed by careful rinsing to remove any trace of the poison. See a veterinarian if skin irritation worsens, especially if oozing sores develop. Dogs who have ingested the plant and show clinical signs may require hospitalization, intravenous fluids and activated charcoal to absorb any residual plant material in the stomach.
Even though most dogs appear to be resistant to the toxic effects of poison ivy, be careful in woods or areas with undergrowth if you have a short-furred dog or one prone to eating plants.