A Canadian scientist is warning that combining sunscreen and potent bug sprays containing DEET may be harmful, especially to children.

The double threat of the blazing sun and West Nile virus has many parents scrambling to protect their children this summer.

But, a new study by Dr. Xiaochen Gu of the University of Manitoba is warning of possible side effects when sunscreen and DEET are used together on kids.

The effects can be as minor as headaches and rashes or as major as seizures and hypertension.

Sunscreens and mosquitos repellents are designed to stay on the surface of the skin, but Gu's research found that when the two products are used together the skin absorbs them at a higher rate than usual.

The effect may be more pronounced in children because their skin is thinner than adults' and will more rapidly absorb chemicals.

"We see absorption amounts increase by 80 per cent and 200 per cent for DEET. This is a total undesirable feature," Gu said.

Gu is trying to modify the non-medicinal ingredients found in sunscreens and repellents to reduce the increased absorption rates, but he has some advice in the meantime.

"You can use (DEET), but especially for young children, just maybe put it on sleeves and clothes ... use it on top of the clothes," he said.

Dr. Steve Coyle says one study isn't enough to convince him. He says people have been using both products for years and to date there have been only 40 cases in Canada of people suffering a severe reaction to DEET.

"If that was the case, children using sunscreen and DEET, we would have expected to see more cases and that really hasn't been the situation," he told CTV News.

Health Canada has already raised concerns about DEET. Bug sprays with a concentration of more than 30 per cent will be banned next year, but there has hardly been a word about DEET and sunscreen combined.

Digging deep on Health Canada's Web site finds the government has asked manufacturers to stop selling products combining DEET and sunscreen.

Sunscreen needs to be applied more often than DEET, so a combination of the two just does not offer protection from dangerous ultraviolet rays, according to Health Canada.

With a report from CTV's Jill Macyshon