Health Canada says it is taking a closer look at the safety of benzocaine products, in light of reports of odd and sometimes dangerous reactions to the pain reliever.

It's also reminding caregivers about risks associated with use of topical benzocaine products, including a rare but potentially serious blood condition known as methomoglobinemia.

Benzocaine is found in some common over-the-counter anti-itch creams, sprays to relieve pain from sore throats, creams to relieve the pain of burns, insect bites, and hemorrhoids, as well as in mouth gels for teething and toothache pain as well as canker sores and irritation of the mouth.

They are also used during surgical and dental procedures to numb the mouth and throat.

The agency says it first warned about the small but serious risk of methemoglobinemia, or MetHb, in November 2006. MetHb is a condition in which red blood cells suddenly lose the ability to deliver oxygen throughout the body. In the most severe cases, methemoglobinemia can result in death.

Health Canada says it has since received seven reports of serious adverse reactions linked to topical benzocaine -- including four reports of MetHb.

It warned caregivers and users of benzocaine products to watch for the signs and symptoms of MetHb, which can include pale, grey- or blue-coloured skin, lips, or nail beds; shortness of breath; fatigue; confusion; headache; lightheadedness; nausea; and change in heart rate.

"These symptoms can appear within minutes or one to two hours after benzocaine use, and can occur after the first or several uses. In rare severe cases, MetHb can progress to stupor, coma and possibly death," the agency said in a statement Tuesday.

Other reported side effects associated with topical benzocaine products include breathing or swallowing difficulties, a swollen tongue or mouth, irregular heartbeat, malaise, body twitching, hypersensitivity, burning, redness, itching, rash and irritation at the site of administration.

These side effects can occur to anyone who is sensitive to benzocaine, and can occur regardless of the type of product used or the strength of the benzocaine concentration.

Anyone experiencing symptoms is advised to seek medical attention, Health Canada said.

To report suspected adverse reaction to these or other health products, please contact Health Canada's Canada Vigilance Program toll-free at 1-866-234-2345, or complete a Canada Vigilance Reporting Form

The Food and Drug Administration issued a similar warning earlier this month when it noted that it continues to receive reports of MetHb.

It advised against using benzocaine products on children less than two years of age, except under the advice and supervision of a healthcare professional.