I have used it on my 10 month old, he is now 6. I did a double dose on a flight to South Africa. He slept for about 8 hours. My advice is to wait until they are quite tired, or in a place where they are unable to run around - ie already in the aeroplane and give it then. On some children it can make them a bit hyper esp if they have the chance to run around. I would try it at home first and check the child sleeps - even try on an evening when putting him/her to bed. Other thing, you will be asked the age of the child when buying it over the counter - you need to say the child is over two. I hope that helps.