Baking soda should not be applied directly to flea bites as you will see very little relief from your symptoms from this method.
Baking soda is good however, as a home remedy for killing fleas because it has a dehydrating effect on fleas and can kill them shortly after contact.
Many people spread baking soda in the carpet of a home that is infested with fleas, hoping that the fleas will come in contact with the substance.
You can also give your dog a bath in water that has baking soda added to it in order to coat the skin with a thin solution, which will have the effect of repelling and killing fleas.
There are better products available on the market to use for flea control than baking soda. Specifically there are professional flea powders and flea shampoos that have been formulated with pesticides and other chemicals that are much more effective at killing and controlling fleas.
But if you do not have access to such products for whatever reason, or you simply wish to try a home remedy, you may try baking soda for flea control.