Which is better in killing fleas backing soda or borax?

Both baking soda and borax can be effective in killing fleas, but borax is generally considered more potent. Borax works by dehydrating fleas and disrupting their life cycle, while baking soda can help by absorbing moisture and potentially dehydrating them. However, caution should be exercised with borax, as it can be toxic to pets and children if ingested. For flea control, a combination of methods, including vacuuming and professional treatments, is often recommended.