Between birth and 18 months, babies may have as many as 15 injections. It is not certain whether babies feel pain in the same way as older children and adults, or whether they are simply unable to express it. Recent evidence has proven they do feel pain and efforts have been made to reduce pain caused by injections through the use of medicines, creams, pacifiers and distraction techniques. One simple alternative that is increasingly recommended is the use of a syringe or dropper to put a few drops of a sugary solution in a child's mouth. The sugar may help to reduce pain by triggering the release of pain-relieving chemicals in the body or by contacting taste receptors that induce feelings of comfort.

The researchers reviewed data from 14 studies involving a total of 1,551 infants aged between one month and a year. Most studies compared sucrose, given two minutes before immunisation, with water. Overall, babies given the sugary solution cried for a shorter time than those given water even though the results of the studies varied. Individual studies also used different pain measures, making it difficult to conclude that sugar solutions actually reduced pain.

"Giving babies something sweet to taste before injections may stop them from crying for as long," said lead researcher Manal Kassab of the Department of Maternal and Child Health at the Jordan University of Science and Technology in Irbid, Jordan. "Although we can't confidently say that sugary solutions reduce needle pain, these results do look promising."

Individual studies also used varying strengths of sugar solution. The researchers say future studies should examine the effects of different concentrations.

"We need to see more data from well-conducted trials in children under one year, especially in relation to optimal concentration, volume and method of administration of sugar solutions," said Kassab.