I personally like Tavist - D (tm), which also contains a decongestant, since I think some dogs are bothered by an inability to equalize the pressure in their ears when they have blocked eustachian tubes from allergies. (vetinfo.com)
Young kids also have more horizontal Eustachian tubes (channels that connect the middle ear to the throat), allowing fluid to collect instead of drain. (webmd.com)
Changes in cabin pressure can be painful, especially for younger children with smaller eustachian tubes (a tube in the ear that helps even out pressure) and children with a cold. (caringforkids.cps.ca)