© Depositphotos.com/Bruce MacQueen
Contact with the venom does not generally cause too much of a problem. A nettle or poison ivy-type rash often occurs, which can range from mild with slight reddening of the skin, to burning, swelling and pain, none of which should keep you away from your gardening duties for too long. Hypersensitive individuals may, of course, experience more severe symptoms that could include swelling and nausea.The warning message claims that the caterpillars are "new to the area". However, it does not state which region, or even which country, the "area" pertains to. The hickory tussock moth caterpillar can be found in southern regions of Canada, and in the south-western and north-eastern United States. I could find no reports that suggest that contact with caterpillars are currently causing significantly more doctor visits or hospitalizations than they have in the past.
Caterpillars or larvae of certain moths possess stinging hairs. These sharp hairs or spines are either hollow, connected to poison glands (venom flows on contact), or similar to glass fibers (hairs break off in skin easily) sometimes causing pain like a needle prick. Depending on the individual, reaction to the sting ranges from mild, with local reddening, swelling, burning and itching to severe pain. Hypersensitive persons may experience severe swelling, nausea and generalized systemic reactions, occasionally requiring hospital treatment. In severe cases, entrance of hairs into the eye can cause blindness.
In 2013, another message began circulating that described an incident in which a child touched a white caterpillar and experienced swelling and a rash. The message notes:
Just to give all you parents a heads up.....Evan pet a white caterpillar this weekend and within 10 minutes his finger swelled up and this happened. These caterpillars are poisonous...alive AND dead so please caution your kids and tell them DONT touch caterpillars.
The message includes an image depicting how the child was affected. The message does not give enough details to identify the species of caterpillar that cause the child's reaction. However, it may well have been a hickory tussock moth caterpillar
Many youngsters - my much younger self included - have found out the hard way that playing with cute hairy caterpillars is not a wise move. In Australia such caterpillars are often colloquially referred to as "itchy grubs" for obvious reasons. As noted above, reactions to hairy caterpillars can sometimes be quite serious. But, most of the time, some basic rash first aid and a good cuddle from mum is enough to set things right.
Last updated: September 30, 2013
Officials: black and white caterpillars are not poisonous, but can be allergenic
Hickory Tussock Moth
Species Lophocampa caryae - Hickory Tussock Moth
Ohio State University Extension Fact Sheet