What does Epsom salt do to mice?

Epsom salt, which is magnesium sulfate, does not reliably kill or repel mice and is not considered an effective mouse control method by pest control professionals, despite many internet claims that it is a natural deterrent or poison. Some websites suggest sprinkling Epsom salt around entry points, in gardens, or mixing it with food to dehydrate or poison mice, claiming that the strong taste or magnesium will harm them. In reality, Epsom salt has very low toxicity to mice and rats when ingested in small amounts, and mice will generally avoid eating large amounts of it because of its bitter taste, so it does not work as a poison. As a repellent, its effect is minimal and temporary, mice have sensitive noses but Epsom salt does not have a strong pungent odor like peppermint oil that irritates them, and they will simply walk around or over it if food and shelter are available. Ingesting very large amounts of Epsom salt can cause diarrhea and dehydration in small animals due to its laxative effect, but it is not a quick or humane kill and is dangerous to use around pets, children, and wildlife. The most effective methods remain sealing holes larger than a quarter inch with steel wool and caulk, storing food in airtight containers, removing clutter, and using snap traps or electronic traps baited with peanut butter.