Salt doesn’t kill fleas. Few credible sources mention using salt for flea control. They state to apply it outdoors and subsequently spray it down with water. This method wouldn’t work inside homes. Despite the lack of evidence, some unreliable sources claim sprinkling salt on carpets will kill fleas. This claim is doubtful.
Salt for Killing Fleas
A handful of reliable sources mention using salt to kill fleas. These documents date back to the early 1900s, a time well before modern insecticides. They suggest applying salt to the ground, and then thoroughly spraying it down with water. Alternatively, sea water can be used. As the saltwater dries, moisture is removed from the area, which ultimately desiccates and kills any fleas.
This method is only done outdoors, often inside the pens of horses, hogs, or poultry. It can also be done on dirt-floor basements.
Using Salt within Homes
There’s no literature, nor any studies, that mention using salt to kill fleas indoors. Uncited books, websites, and YouTube videos sometimes recommend using salt on carpets to kill fleas. However, these suggestions are unfounded. They’re most likely pandering to the recent trend of “natural” control solutions, with little evidence backing up their claims.
Adult fleas permanently live on their host. Thus, attempting to kill adult fleas by applying salt to the environment isn’t feasible. Plus, adults make up less than 5% of an infestation. Immature stages must be targeted to end an infestation.
Eggs and larvae develop in the environment, primarily carpeting in homes. Based on the literature, salt would need to be sprinkled in the environment and then thoroughly soaked with water. Obviously this is a poor control method indoors, as wet carpets will lead to other problems, such as mold. Furthermore, the carpet canopy creates a micro-habitat within fibers. Humidity and temperature and kept relatively high and stable. Salt probably won’t alter the flea environment much, unfortunately.
Salt’s Crystalline Structure
Salt is sometimes compared to diatomaceous earth (DE) in regards to flea control. This is a poor comparison, as these substances have completely different structures. Salt has a crystalline structure, while DE is a powder (amorphous silica). In fact, DE used for pool filters (crystalline silica) doesn’t work for pest control precisely because it’s heated to the point of becoming crystalline. As a result, it loses its absorptive powers and ability to desiccate insects.