Sucking on hair is common among youngsters. It’s mostly harmless, but the habit can become risky if the child ingests hair — especially a lot of it. Some kids may eat so much hair that it forms a hairball in their stomach, referred to as a bezoar — a mass of foreign material in the stomach — and if large enough, it can cause a pain and stomach obstruction. “Occasionally a hair bezoar can become so large through accumulation of food and gum, that an operation is needed to surgically remove it,” says Teach.