A visitor to Bayside learned the hard way that invasive browntail moths are moving into the Midcoast.

A few days into her stay earlier this month, Lisa Green of Boston's North End developed a stinging, itchy rash that began to spread from her waist up her back. "It started Monday," she said. "When it got worse Tuesday, I went to the Emergency Room."

Waldo County General Hospital ER staff quickly identified the rash, which by then was appearing on her arm as well, as a reaction to contact with the toxic hairs found in browntail moth, or “BTM,” cocoons. "They said they've seen a lot of this," Green said. “And apparently some people are more sensitive to it than others.”

Maine's Department of Agriculture, Conservation and Forestry has been issuing warnings since March about the pests and the danger of coming in contact with the cocoons found in trees, wrapped in leaves, under outdoor furniture, in gutters, under rafters and porch floor joists, on boats and firewood — even underneath cars, which are one means by which infestation travels.

The cocoons are full of hairs from the moth larvae. They can be picked up from direct contact or can become airborne. The rash they cause, similar to that of poison ivy, can last a few hours, a few days, or — in highly sensitive people — several weeks. Exposure can also lead to respiratory distress, which can be serious.

Green had visited a friend's home the day before and believes she picked up the toxic hairs while sitting on the porch. Medicines prescribed by ER staff (prednisone, ointment and what she described as “a kind of high-test Benadryl”) relieved her symptoms in a few days.

“The hairs stay in your clothing,” she said, “so I washed everything several times to make sure they were all out. They stay with you and move through your clothing when you toss a sweater or other things on a chair, or go to bed — so I washed our sheets, too!”

Unfortunately, Green said, she couldn’t put on a bathing suit, and was prohibited from going in the water or being in the sun until she finished her treatment.

Asked about similar cases in Waldo and Knox counties, a hospital spokeswoman said in an email that MaineHealth is “not actively tracking cases” and cannot provide that specific data.

“We can say that at (Pen Bay Medical Center) we have seen an increase in cases in the emergency department,” Jenifer Harris wrote in an email. However, she wrote that WCGH reports “very little BTM activity at this time.”

Accidentally introduced into Massachusetts more than a century ago, browntail moths gradually spread all over New England, then receded until they were found primarily on Cape Cod and Maine islands.

Now they are moving inland and expanding their footprint, according to Maine Department of Agriculture, Conservation and Forestry. Browntail moths today are found in varying population densities over more than 6,500 square miles of Maine, from the coast inland.

The caterpillars are identifiable by two red dots on their backs. Don't touch them or pick them up. The moths have white wings, tufts of white hairs about their heads, and brown tails. Their hairs remain toxic for three years.

The DACF website lists methods that can help stem the pests' resurgence. One way is to clip the overwintering webs and destroy them by either soaking them overnight in soapy water or burning them. Best time to do this is in winter or early spring (until mid-April). Wear protective clothing, and wet down the cocoons before removing them.

Cocoons or caterpillars crawling on buildings can be removed with water from a high-pressure hose.

Browntail moth infestations also can be controlled with pesticides applied by a licensed applicator. Pesticides should be used when caterpillars are small and feeding ― usually before the end of May. Timing is critical: Treatment before the end of May will prevent development of the toxic hairs; treatment after the end of May will result in dead caterpillars and toxic hairs. Undertaking control measures early will reduce the chance of exposure to the irritating caterpillar hairs.

Maine Forest Service maintains a list of pesticide applicators licensed and certified to treat browntail moths and other tree pests. It is available by calling 207-287-2431, emailing patti.roberts@maine.gov or visiting maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_pesticide_applicator_info.htm.

As for Lisa Green’s family, her ER visit was not the only one during their week-long stay in Bayside, where they’ve vacationed for the last six years. Her son Liam Faller, 10, stepped on a piece of glass on the Fourth of July, necessitating a return trip that night.

It was well-timed, she said; the Emergency Room was empty after what had been a busy day.

“Everybody was super nice,” Green said. “There was even someone from the North End working there!”

For more information about browntail moths, visit https://www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm.

For tips on precautions to take when doing yard work or opening a cottage for the summer season, visit https://www.maine.gov/dacf/mfs/forest_health/insects/browntail_moth_precautions.htm.