Rodent articles · Updated
Do rodent repellents work? Ultrasonic plug-ins, peppermint oil and more
We haven't seen good evidence that ultrasonic devices, peppermint oil, dryer sheets or similar repellents keep rats or mice out of a house for long. Food storage, trapping and sealing the gaps do.
Short answer: we haven't seen good evidence that repellents keep rats or mice out of a house for long. That goes for ultrasonic plug-ins, peppermint oil, dryer sheets and most of the scent products on the store shelf. Rodents may avoid a new smell or sound for a little while, then get used to it, especially if there's food on the other side.
What works is plainer: take away food, trap the ones inside and seal the gaps. Here's a closer look at the popular repellents and what to spend the money on instead.
Ultrasonic plug-ins
These plug into an outlet and send out high-frequency sound that people can't hear. The pitch is that rodents hate it and leave. The trouble is that the sound doesn't pass through walls, furniture or insulation, so it doesn't reach most places rodents live. And animals tend to get used to a steady noise. Angi lists ultrasonic emitters at $40 to $60. That money buys a lot of snap traps and a garage door seal.
Peppermint oil and other scents
Peppermint oil on cotton balls is the most common home remedy. The smell fades within days, and a hungry mouse will walk past it to reach a bag of dog food. Commercial scent repellents work the same way. Angi lists scent repellents at about $10 or more. They won't hurt, but don't count on them, and don't skip the real fixes because you put out a few cotton balls.
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Mothballs and dryer sheets
Mothballs are a pesticide, sold with label directions for clothes storage. The fumes aren't something you want in an attic over your bedrooms or in a closed garage, and they don't seal anything. Dryer sheets are a popular trick for keeping mice out of cars and stored boats. People report mixed results. A car that gets moved and a garage with a tight door work better.
Predator urine and cats
Predator urine products are sold for gardens. Results are inconsistent, and they wash away in the first rain. A cat may catch some mice, and the scent of a cat can make mice more careful. Neither one closes the hole the mice are using. Plenty of San Antonio homes with cats still have roof rats in the attic.
What to spend the money on instead
These cost about the same as a couple of plug-in repellents and do far more:
- A dozen snap traps, set along walls where droppings are
- Metal cans with lids for pet food, bird seed and feed
- A new garage door bottom seal
- Door sweeps on side doors
- Weep hole screens for the bottom row of brick
- Copper or stainless mesh for pipe and line holes
Why repellents seem to work at first
Rats and mice are cautious around anything new, a habit called neophobia. A new smell, a new device or a new object in their path can make them hold back for a few days. That's often when people decide the product worked. Then the rodents get used to it, especially if food is close by, and the activity returns. By then the receipt is in the trash.
The same thing happens when people move things around in a garage or attic. Activity may dip for a night or two simply because the space changed.
Owls, cats and natural predators
Barn owl boxes and outdoor cats come up a lot in conversations about natural rodent control. Predators do eat rodents, but they don't seal the gap in your soffit or keep mice out of a garage with a worn door seal. A house with an open entry point and a food source will keep attracting new rodents no matter what's hunting in the yard.
A better plan for the same budget
If you were about to buy a couple of plug-in repellers, spend that money this way instead. Buy a dozen snap traps and set them along the walls where you see droppings. Put pet food and seed in metal cans. Replace the garage door bottom seal. Screen the weep holes you can reach. Then check the traps every morning for a week. That plan costs about the same and gives you a clear answer about whether rodents are still getting in.
When to call someone
If you've tried repellents and still hear rodents, they're living inside and they've found a way in. A technician can find the gaps and seal them, which is the part repellents can't do. See rodent exclusion, and the traps article for what to use in the meantime. For a stored vehicle, the car engine article covers what helps.
Ready to have the gaps found and sealed? Call and describe what you're seeing.
Call (210) 955-2948
Questions from callers
Do ultrasonic repellers hurt pets?
Dogs and cats can hear some high frequencies, and pet rodents like hamsters and guinea pigs may be bothered. Another reason to skip them.
Does steel wool count as a repellent?
No, it's a barrier. Packing a hole with metal mesh blocks it physically. Copper or stainless mesh lasts longer than steel wool in humid weather. See steel wool vs copper mesh.
Will a repellent push mice out of the walls?
Not reliably. Mice in walls are best handled with traps where they come out and sealing where they get in.
Do ammonia or vinegar keep rats away?
We haven't seen good evidence that they do for long, and strong fumes in a closed attic or garage are unpleasant for people and pets.