Should I Use Poison to Kill Mice?

UNH Cooperative Extension states plainly that trapping is preferred over rodenticides for most homes: trapping eliminates the risk of accidentally poisoning children and pets and lets you account for and physically remove the dead mouse. A poisoned mouse, by contrast, may die out of sight inside a wall void or ceiling, where it can cause days to weeks of odor and attract flies, with no way to retrieve it without opening the cavity — or it may be eaten by another animal, sickening it.

This isn't a hypothetical concern. Necropsies by the NH Veterinary Diagnostic Laboratory at UNH found the large majority of animals tested from around the state had been exposed to rodenticides, often long-acting second-generation anticoagulants, and NH Audubon has documented several poisoned bald eagles in the past five years. The EPA restricts these second-generation anticoagulants to professional and agricultural use and requires tamper-resistant bait stations wherever children, pets, or wildlife may be present specifically because of risks like these.

Extension guidance reserves rodenticides for large or inaccessible infestations where trapping alone can't keep up, and advises against using toxicants at all where young, elderly, or medically vulnerable people live. In those cases, a licensed applicator can select the right product and place it in a tamper-resistant station, minimizing odor, secondary poisoning, and non-target exposure — a meaningfully different risk profile than a homeowner scattering loose bait.

UNH Extension and the CDC's 'Seal Up, Trap Up, Clean Up' guidance both point the same direction: seal entry points, trap the mice already inside, then clean up safely. Poison sits at the end of that sequence, not the front — a situational tool for cases traps and exclusion genuinely can't solve, ideally applied by a professional.