Children's feet change with age. Shoe and sock sizes may change every few months as a child's feet grow.
Shoes that don't fit properly can aggravate the feet. Always measure a child's feet before buying shoes, and watch for signs of irritation.
Never hand down footwear. Just because a shoe size fits one could comfortably doesn't mean it will fit another the same way. Also, sharing shoes can spread fungi like athletes foot and nail fungus.
Examine the heels. Children may wear through the heels of shoes quicker than outgrowing shoes themselves. Uneven heel ear can indicate a foot problem that should be checked by a podiatrist.
Take your child shoe shopping. Every shoe fits differently. Letting a child have a say in a the shoe buying process promotes healthy foot habits down the road.
Always buy for the larger foot. Feet are seldom precisely the same size.
Buy shoes that do not need a "break-in" period. Shoes should be comfortable immediately. Also make sure to have your child try on shoes with the socks or tights, if that's how they'll be worn.