Hospitals in Montreal are warning parents to take extra precautions after they say they treated several cases of “severe” frostbite.

Sainte-Justine Hospital posted a warning on Facebook with a photo that shows severely blistered feet. “Young children are particularly at risk,” the hospital said.

The Montreal Children’s Hospital says it too has been treating frostbite during the recent cold snap.

Health Canada explains that frostbite occurs when blood vessels close to the skin constrict to protect the core body temperature.

Mild frostbite, sometimes called frostnip, makes skin look yellowish or white but it is still soft to the touch, Health Canada says.

Severe frostbite can cause hard, black skin that blisters. It can lead to nerve damage and even the loss of limbs.

Liane Fransblow, who works in injury prevention at the Montreal Children’s Hospital, offered the following tips for parents to prevent frostbite:

  • Keep children indoors as much as possible if it’s colder than -20C outside.
  • Check children frequently for numb skin and changes in skin colour. Pay particular attention to ears, noses, hands and feet.
  • Remember that some children won't want to tell parents or caregivers about suspected frostbite because they don't want to stop playing and go inside.
  • If children are playing outside in freezing temperatures, bring them inside to warm up every once in a while.
  • Bundle children up with neckwarmers, hats, gloves, mittens and layers of clothing.
  • Make sure there are no holes in children’s boots so snow doesn’t get inside.

Franslow says that people with “waxy, hard skin” or blisters should go straight to an emergency room, since those are signs they have severe frostbite

People with only numbness or loss of colour can warm their skin with warm but not hot water. Health Canada advises the water should be just above body temperature. Do not rub, massage or shake the injured skin because that can cause more damage.

Seek medical attention if symptoms don’t resolve within an hour, Franslow says.

With files from CTV Montreal