Many children receive the treatment even though doctors do not know how effective it is or whether it is even needed.

In Denmark three out of ten children receive grommets before their fifth birthday to treat a middle ear infection. Denmark has the highest rate of surgical treatment with grommets among children in the world.

Each year, doctors conduct more than 60,000 procedures, and three out of ten children have undergone the procedure before the age of five. Apart from the cost of surgery there is little scientific evidence that the procedure works as a treatment for middle ear infection.

Several studies indicate that the infection usually clears up with or without treatment by grommets. The basis for grommet surgery in children seems thin and many Danish scientists are now rethinking the practice. A 2010 Cochrane analysis (a review of existing research) demonstrated that the procedure was effective in the long-term in one out of every three to five children with recurrent middle ear infection.

One of the criteria for surgical grommets is that that children’s hearing is affected. But it is impossible to conduct reliable hearing tests on a child under the age of three or four, says Ovesen.

Practitioners can recommend grommet surgery for a child if they have fluid in their middle ear for at least three months. However most children under the age of three will experience this at some point. And the fluid can develop and disappear in a short period, says Ovesen.

“The trick is to find out when this is a health problem or results in persistent symptoms for the child,” she says.

According to Hellström, fluid in the middle ear does not necessarily lead to hearing problems. Although in some children it can severely impair their hearing and their ability to communicate. So how do you decide which child will suffer if grommet is not inserted.

Danish rules clearly state that a doctor or consultant should not refer the child for grommet surgery until three months after they were first presented, in order to investigate whether they have hearing difficulties.

But this can be difficult to communicate to parents “They feel quite pressured to insert grommets because the child is in pain and the parents are worn thin,” he says.

“We also feel it as scientists. We’re now studying children with and without grommets. If the children who don’t have grommets still have problems one month later, then those children will receive grommets anyway, because otherwise the parents refuse to participate. There’s a whole culture around grommets here in Denmark,” says Homøe.

Even though the science and national guidelines show that Denmark may be over reliant on grommets, scientists are not discouraging the treatment.

Oversen notes that middle ear infections disappear by three years of age among 90 per cent of all affected children. But for the other ten per cent it could be unhealthy to be left untreated for so long, she says.

Based on a report by Thomas Hoffmann in Science Nordic