A spray meant to knock out an invasive species is causing a lot of concern for residents in the Cloverdale area of Surrey, who say they weren’t notified their properties were in the spray zone.

Dina Neil says she took her son to the hospital when he developed an allergic reaction after playing outside in the neighbourhood that was sprayed with a biological insecticide called Foray 48B.

“He couldn't eat dinner,” Neil said. “His throat was highly irritated, so he was coughing and i took his shirt off and he had angry hives all over his body.”

Foray 48B is meant to eradicate the gypsy moth caterpillar, which is an invasive species in British Columbia and can pose a threat to trees.

It’s been sprayed from low-flying helicopters in Cloverdale on several mornings this month, and is scheduled to be deployed again Monday through Thursday.

B.C.’s Ministry of Forests maintains that the insecticide is safe, and the provincial government’s Health Link website has a page dedicated to explaining the product and its uses.

“There is nothing toxic in that product,” forest health officer Tim Ebata told CTV News by phone. “It's been heavily evaluated.”

Indeed, two public health studies in Vancouver and Victoria found no “increase in illnesses seen by health care providers or in hospital emergency room visits due to spraying,” according to the Health Link site.

“The pest management regulatory agency considers this spray safe for using over urban areas,” Ebata said.

Still, the label for the product -- available on the website of Valent, the company responsible for its distribution in Canada -- advises users to “avoid contact with skin, eyes, and clothing,” and to “seek medical attention” if irritation persists or is severe after exposure.

Robert Jirava said some of the people in his neighbourhood have reported health problems since the spraying began, and his own asthma has been acting up.

“I find it hard to imagine that's a coincidence,” he said.

Jirava said he wasn’t aware that spraying was scheduled to take place over his house until it happened.

“We were awoken by a loud thunderous noise early one morning and my wife was running around the house in a bit of panic shutting all the windows because they were spraying something on us,” he said.

Ebata told CTV News there was some notification of residents before the spraying began, but that the ministry is now trying to do more -- setting up highway signs and getting flyers delivered.

Anyone concerned about potential exposure to Foray 48B can avoid it simply by staying inside, Ebata said.

“We are recommending that if you want to avoid direct contact with the droplets that are being deposited from the air that you just stay indoors for up to half an hour,” he said.

With files from CTV Vancouver's Maria Weisgarber