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The Brown Tail Moth (BTM) is an invasive species found only on the coast of Maine and Cape Cod. This moth is an insect of both forest and human health concern. The BTM has been declared a Public Health Nuisance by the Maine Centers for Disease Control and Prevention (CDC).
The BTM caterpillar has tiny poisonous hairs that cause dermatitis similar to poison ivy on sensitive individuals. People may develop dermatitis from direct contact with the caterpillar or indirectly from contact with airborne hairs. The hairs become airborne from either being dislodged from the living or dead caterpillar or they come from cast skins with the caterpillar molts. Most people affected by the hairs develop a localized rash that will last for a few hours up to several days but on some sensitive individuals the rash can be severe and last for several weeks. The rash results from both a chemical reaction to a toxin in the hairs and a physical irritation as the barbed hairs become embedded in the skin. Respiratory distress from inhaling the hairs can be serious. Caterpillars are active from April to late June. Hairs remain toxic throughout the summer but get washed into the soil and are less of a problem over time.