This condition occurs commonly in young children during winter nights. The child may appear well during the daytime except, possibly, for a slight cold. The attack awakens the child from sleep and alarms the parents because of the child's difficulty in drawing air into his lungs and because of the barking cough. There may develop a bluish tinge about the child's lips and at the base of his fingernails.
WHAT TO DO
1. Wrap the child in a warm blanket and hold him upright over your shoulder while making ready the treatment outlined below.
2. Take the child into a small room or into the kitchen and fill the room as quickly as possible with steamy air produced by a stream of hot water running into the sink or by the vigorous boiling of a pan of water. Keep the room and the child warm.
3. Once the child's breathing has returned to normal and while he is still in the warm room, apply to his chest a so called "heating" compress.
4. Leave this compress in place for the rest of the night. Arrange for an adult to sleep in the same room with the child until morning and, perhaps, for the next few nights. This adult should check on the child's breathing occasionally and should be alert for any worsening of his condition, which might indicate bronchitis or pneumonia. In this case call a physician immediately.
Source
Modern Medical Guide
Harold Shryock, M.D