Usually the stinky smell comes from bacteria inside the boot that love the damp environment. Often, the bacteria come off of the skin of the wearer. Make sure your child’s feet get clean in the bath.
There are many creative ways to quell the odor. First, if your son’s boots have a removable lining, take it out, wash it, then air dry. If not, you could use a sock or a muslin bag and put baking soda in it with some tea tree essential oil. Leave overnight. There are also many boot sprays on the market that can eliminate odor.
A better solution may be to purchase a boot with an antimicrobial lining like this one on our list: Stride Rite Made 2 Play Sneaker Winter Boot.