What smell is toxic to mice?

Most smells that repel mice are not truly toxic but simply irritating to their sensitive noses, and truly toxic fumes are dangerous to humans and pets as well and should never be used in a home. Common strong smells like peppermint oil, eucalyptus oil, cloves, ammonia, and vinegar irritate mice and may cause them to avoid an area temporarily, but they are not toxic at the concentrations used on cotton balls and they do not kill mice. Some essential oils can be toxic to mice if ingested in large concentrated amounts or inhaled in very high concentrations in an enclosed space, for example tea tree oil, pennyroyal oil, and undiluted peppermint oil can cause liver damage, breathing difficulties, and nervous system effects in small rodents if they are forced to breathe heavy vapors or ingest it, but using them that way is unsafe for humans, cats, dogs, and other animals too. Commercial rodent repellents that contain predator urine are not toxic, just odorous. True toxic gases like carbon monoxide, bleach mixed with ammonia creating chloramine, or phosphine are extremely dangerous and illegal and unsafe to use for mouse control. The safest and most effective way to kill mice is not through toxic smells but through approved snap traps, electronic traps, or professional rodenticides used in tamper-resistant bait stations by licensed professionals following safety regulations.