When is thumb-sucking a problem?

Candice Rogerson of Owen Sound, Ont., knows what it’s like to have a thumb-sucker on your hands. “When my son Jonah was little, his thumb was there when I wasn’t able to nurse or cuddle, and he’d suck it when he was tired,” she says. She expected he’d stop once he started school, but raised eyebrows had little effect on this confident kid. “People would comment, and he’d take his thumb out if I asked. But he’d start again—it was his comfort. As long as he wasn’t anxious about it, I decided not to be either.”

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“All babies suck on fingers or objects, to explore the world and for comfort,” says Sarah Hulland, a paediatric dentist in Calgary. And while many parents are initially relieved when their baby finds his thumb (no need to scramble for a soother!), attitudes often change as their child grows up but doesn’t outgrow the habit.

When is it a problem?

According to Hulland, most children stop sucking their thumbs on their own between the ages of three and five, as they learn other ways to soothe themselves, or experience social pressure. But if they continue after their permanent teeth come in, it can cause dental problems, such as buckteeth. “Children who suck vigorously might remodel their jaws and upper palates, due to pressure on the teeth and roof of the mouth,” Hulland says.

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Cheryl Arkison, of Calgary, realized her daughter, Mila, was developing an overbite soon after she started sucking her thumb at age one. “At Mila’s first dental appointment, the dentist told us to start saving money because we’d need it to correct her teeth later,” she says.

That wasn’t the case for Jonah, whose teeth were fine when he quit on his own at age seven. Holland explains that some kids suck gently and infrequently, or just rest their fingers in their mouth, which is less likely to cause damage.

Should you set a quit date?

Most dental changes correct themselves when thumb-sucking stops. You can help kids kick the habit with positive reinforcement, like reward charts, as permanent teeth start coming in. Hulland also recommends moulded thumb guards, which limit the ability to suck. Unpleasant-tasting sprays are another idea. If all else fails, talk to your dentist about inserting a dental device to act as a physical barrier.

In Arkison’s house, it took a cut on Mila’s thumb—or more specifically, the bandage applied to it—when she was three, to help her stop. “That worked for her, but now I have a thumb-sucking 18-month-old son,” she says ruefully. “We’ll see how things go with him!”

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A version of this article appeared in our February 2014 issue with the headline "Thumb war," p. 28.