Why are candies served before an aircraft takes off?

When an aircraft takes off, some passengers often experience a crackling sound in the ears or get earache. The reason is that the inner ear does not adapt itself quickly to the lower air pressure caused by the take-off. A simple candy helps in avoiding this discomfort because while sucking a candy, we need to swallow often. This helps the small muscles to expand the connection between the ear and the nose. In a way, they are ventilated. This leads to a quicker adaptation of the inner ear to the outer air pressure and reduces the pain.