What smells do rats and mice hate?

The smells people try

Most home remedies are strong scents that people expect a rodent to dislike:

• peppermint oil on cotton wool balls, the most common suggestion for mice
• chilli or cayenne sprinkled along runs
• ammonia or used cat litter, meant to smell like a predator
• cloves, eucalyptus and other essential oils
• moth balls, which are made for clothes moths in closed drawers, not for rodents

Use any shop product only as its label says. Guidance on rodenticides (rat and mouse poisons) from the Health and Safety Executive (HSE) says to always follow the product label.

Why a smell will not clear rats or mice

There is no reliable evidence that a scent drives out rats or mice that have already found food and a warm nest. Oils evaporate within days, so the smell fades just as the animals get used to it. A rat that is fed and sheltered has every reason to put up with a smell, and a nest in the wall or under the floor is out of reach of anything you can sprinkle.

The official advice starts somewhere else. HSE's guidance on rodents puts good hygiene, physical barriers and traps first, before any poison.

Where a scent can help a little

A strong smell can make a cupboard you have just emptied and cleaned less inviting while you seal the gap behind it. Treat that as a stopgap of a few days, not a treatment. Keep concentrated oils away from children, and ask your vet before using them where a cat or dog lives.

What really keeps rats and mice away

Sheffield City Council's advice on rats is a good checklist, and the same steps keep mice out.

Sheffield notes that a rat can squeeze through a gap of less than 2.5 cm, and that mesh with holes no larger than 2 mm stops mice using an air brick. Never block an air brick: cover it with mesh so the house can still breathe.

Gadgets and poison

Plug-in sound devices are the other popular deterrent, and the evidence for them is no better. Our guide to ultrasonic pest repellers sets out what regulators found.

If you use poison, buy a consumer product and keep it in a tamper-resistant bait box, as HSE and council advice both say. Sheffield advises against loose bait outside, because birds, squirrels and pets can eat it. Rodents that die in walls or under floors leave a smell, so snap traps are usually the better choice indoors. The rat DIY guide and mouse DIY guide cover setting traps.

When to stop trying and get help

Call a professional if droppings keep appearing in more than one room, if you hear scratching in the walls or loft, if cables or pipes have been gnawed, or if two weeks of trapping has not stopped the activity. Read about rat control and mouse control, and check what rat control costs.

Many councils still treat rats and mice, some free. Find out what your council offers before you pay a private firm. If you rent and they are getting in through a gap in the building, tell your landlord in writing.