It’s one of those household debates that never seems to go away — can moth balls actually kill rats? They’ve got a strong, chemical smell and are often labelled as dangerous, so surely they’d work on rodents too, right?
If you’ve been searching for a quick, cheap way to get rid of rats, you’re not alone. Many homeowners reach for what’s already in the cupboard before calling professionals. But before scattering moth balls around your home or garden, it’s important to understand how they work, what the law says, and whether they’re genuinely effective against rats.
Let’s uncover the truth about moth balls, their chemical composition, and the science behind whether they can repel or kill rats — and what you should be doing instead for safe, lasting pest control.
What Are Moth Balls (and How Are They Meant to Work)?
Moth balls are small, white or coloured balls traditionally used to keep clothes moths and other fabric pests away from stored clothing, blankets, and textiles. They’ve been around for decades, often tucked into wardrobes, attics, and drawers.
These tiny spheres contain either naphthalene or paradichlorobenzene (PDCB) — two strong-smelling chemicals that release vapours over time. Those vapours act as fumigants that kill moth larvae and deter adult moths from laying eggs on fabrics.
They’re designed for closed storage spaces, where the gas builds up enough to be effective. In open areas like lofts, kitchens, or gardens, the vapour disperses far too quickly to have the same impact.
Legally, moth balls are registered under pesticide regulations only for insect control, not for rodents or mammals. That’s an important distinction — because it means using them for anything else could breach safety laws.
Why People Consider Using Moth Balls for Rats
Rats have plagued homes for centuries, so it’s no surprise that people experiment with household items in an effort to keep them away. The idea that moth balls could kill or repel rats comes from their overpowering odour.
The appeal of strong smells
Humans associate strong chemical smells with toxicity — and for good reason. When you open a container of moth balls, the odour is sharp and unpleasant, almost suffocating in confined spaces. It’s easy to assume that if we can barely stand it, rats must find it unbearable.
Online forums and old-fashioned “DIY pest control” guides sometimes suggest placing moth balls in attics, gardens, or under floorboards to scare rats away. Unfortunately, that advice is based on assumption, not evidence.
The myth of smell-based repellents
It’s true that certain strong smells — like peppermint oil or ammonia — can temporarily disturb rats. They have an extremely sensitive sense of smell, and unfamiliar scents can make them cautious. But rats are clever, persistent animals. Once the odour fades or they realise it poses no real threat, they’ll return.
Moth balls, while potent, don’t release enough vapour in open spaces to affect a rat’s nervous system. So although the smell might make them hesitate briefly, it’s not enough to kill them or drive them out permanently.
What Evidence and Authority Say About Moth Balls and Rats
Several scientific and government bodies, including the Health and Safety Executive (HSE) and the British Pest Control Association (BPCA), have weighed in on this issue. The consensus is clear — moth balls are not approved or effective for rat control.
Scientific findings
The active ingredients in moth balls — naphthalene and paradichlorobenzene — can be toxic to mammals in very high doses. However, in the amounts released by moth balls, the concentration in air is too low to be lethal to rats.
A rat would have to consume multiple moth balls for the dose to be harmful — and most rats are too smart (and too repelled by the smell) to eat them.
Regulatory guidelines
The HSE classifies moth balls strictly for moth and insect protection in enclosed spaces. Using them outdoors, or for rodents, violates the Control of Pesticides Regulations (COPR).
In addition, the RSPCA warns that using moth balls to deter rats could cause suffering without solving the infestation. The chemicals can irritate rats’ eyes and respiratory systems, leading to distress but not death. That’s considered inhumane and ineffective.
So, in summary — yes, moth balls are toxic, but not in the right way or the right concentration to control rats safely or legally.
Mechanisms and Practical Limitations: Why Moth Balls Don’t Reliably Kill or Deter Rats
To understand why moth balls fail against rats, we need to look at how they’re designed to work — and why rats are far tougher opponents than insects.
Why smell alone doesn’t equal elimination
Moths are delicate insects with lightweight respiratory systems. A small amount of naphthalene gas is enough to disrupt their metabolism. Rats, on the other hand, are resilient mammals with advanced organs that process toxins differently.
Even in enclosed areas, the vapour from moth balls disperses quickly and doesn’t reach the lethal concentration required to harm a rat. That’s why you might notice the smell lingering for weeks — but the rats remain completely unfazed.
Rat behaviour and survival instincts
Rats are cautious, resourceful creatures. If they encounter something that smells unpleasant or unfamiliar, they’ll simply avoid it and find another route. Their intelligence makes them extremely difficult to fool with odour-based tricks.
Even if moth balls did create temporary discomfort, the effect would be minimal and short-lived. Rats would quickly learn to work around the smell — especially if food or shelter is nearby.
Health, welfare, and environmental concerns
Perhaps the biggest reason to avoid moth balls is their toxicity to humans, pets, and wildlife. Inhaling naphthalene vapours in poorly ventilated spaces can cause headaches, nausea, and even anaemia with prolonged exposure.
If children or pets accidentally ingest moth balls, the results can be fatal. Dogs are particularly vulnerable because they may mistake the small white balls for treats.
From an environmental perspective, both naphthalene and PDCB are pollutants that can contaminate soil and waterways when disposed of improperly.
What You Should Do Instead: Safe, Effective Rat Control Alternatives
If you’re dealing with rats, don’t rely on moth balls or other home remedies. Instead, focus on safe, proven methods that target the root cause of infestations.
Prevention and proofing your property
The best way to stop rats is to make your home less inviting in the first place:
- Seal entry points: Use metal mesh or wire wool to block holes, vents, and pipe gaps.
- Secure food sources: Store grains, pet food, and birdseed in airtight containers.
- Eliminate water access: Fix leaks and remove standing water from gutters or trays.
- Keep spaces tidy: Cluttered gardens and lofts provide ideal nesting sites.
These simple steps dramatically reduce your risk of attracting rats — and they cost nothing compared to ineffective shortcuts.
Approved control methods
When prevention isn’t enough, move to proven control measures such as:
- Snap traps – Fast, targeted, and humane when used correctly.
- Enclosed bait stations – Hold authorised rodenticides safely away from pets and children.
- Electronic traps – Provide instant elimination with no chemicals.
- Professional pest control – Certified experts use regulated products and methods guaranteed to meet UK safety standards.
The BPCA recommends using professional pest controllers for recurring infestations. They’re trained to assess entry points, locate nests, and apply treatments safely under law.
Eco-friendly and humane approaches
If you prefer to avoid lethal measures, consider live-capture traps paired with professional relocation services. Many pest control companies also follow IPM (Integrated Pest Management) principles — focusing on prevention, monitoring, and minimal chemical use.
Frequently Asked Questions (FAQs)
Are moth balls legal for use against rats in the UK?
No. The HSE only approves moth balls for moth and insect control. Using them for rodents breaches pesticide regulations and may be classed as misuse.
Will moth balls at least keep rats away temporarily?
Maybe — but not reliably. The smell can make rats hesitant, but they quickly adapt or move to unaffected areas.
Can moth balls harm pets or children?
Yes. Both naphthalene and paradichlorobenzene are toxic when inhaled or swallowed. Keep them away from living areas and never scatter them openly.
Do moth balls kill rats if they eat them?
Potentially, but rats rarely eat them. Even if they did, it would cause a slow, painful death, which is inhumane and illegal.
What should I use instead?
Stick with approved traps, baits, and professional pest control services. If you prefer natural deterrents, focus on sealing access points and keeping your environment clean rather than relying on smell-based methods.
Our Final Say
Moth balls have a long history as household pest deterrents — but when it comes to rats, they’re simply not the solution. The idea that their strong chemical odour can kill or repel rodents might sound convincing, but in practice, it’s both ineffective and unsafe.
Rats are smart, resilient creatures that need far more than a smell to stop them. Using moth balls for rodent control is not only illegal under UK pesticide law but also potentially harmful to humans, pets, and wildlife.
If you’re serious about removing rats, invest in methods that actually work. Seal gaps, secure food, and call a professional pest control expert if the problem persists. Safe, legal pest management isn’t about quick fixes — it’s about creating an environment where rats can’t survive in the first place.
Knowledge, not moth balls, is your most powerful pest deterrent.
Pest Control Stanbridge – Pest Control Upper Shelton – Pest Control Cockayne Hatley
