Mothballs are among the most toxic things in an ordinary home, and almost nobody stores them that way. A single one can make a dog or cat seriously unwell, and the effects often appear a day or two late. If your pet eats one, phone Alma Animal Hospital, or an open emergency hospital outside our hours, the same hour.
Why this is an October problem in Dunbar
The wool comes out in October. The summer clothes go into bags, the sweaters come down from the top shelf, the duvet gets swapped, and in a lot of Dunbar and West Point Grey houses that means opening a cedar closet, a basement storage room or a crawl space that has been shut since spring.
These are older homes, many of them with built-in storage, unfinished basements and genuine crawl spaces, and the previous owners left things in them. It is not unusual to find a forgotten box of mothballs in a basement or a crawl space, or a scattering of crystals put down by somebody years ago to deter rodents.
That second use is the one that causes the most trouble. Mothballs placed loose in an attic, a crawl space, a garden bed or under a deck, to put off rats, squirrels, raccoons or cats, are both ineffective and now accessible to a dog or a cat. They are made to be used sealed inside a container with the clothing, not spread around a space an animal can walk into.
What is actually in a mothball
Modern mothballs are usually one of two chemicals, and the difference matters to us.
Naphthalene is the older of the two and roughly twice as dangerous. It damages red blood cells, which means a pet can become anemic a day or two after eating one, and it can also injure the liver and cause seizures. Naphthalene is the more dangerous of the two by a clear margin.
Paradichlorobenzene is more common in newer products. It is less dangerous but still causes vomiting, tremors and lethargy, and a dog who eats several of them is still in trouble.
You cannot tell which is which by looking. The old trick of floating them in salty water is not worth your time now, whether or not your pet seems unwell, because it burns the window where help is most straightforward. Instead, do the useful thing: keep the box, or photograph the ingredient panel, and bring it with you.
Flakes, crystals, cakes and hanging blocks are the same chemicals in different shapes, and some are worse because the surface area is larger. Cedar blocks and cedar balls are a different product entirely and are not mothballs, though cedar oil in any concentrated form is its own irritant, particularly for cats.
Dogs eat them. Cats breathe them.
The two species get into trouble differently, and both routes are real.
Dogs, especially young ones, eat mothballs out of curiosity or because they rolled across a floor and became a toy. One mothball is enough to need a phone call. A dog who found a box and emptied it is an emergency.
Cats are less likely to eat one and much more sensitive to the vapour. A cat shut in a closet, a basement room or a cupboard where mothballs are working away is breathing the vapour continuously, and cats process these chemicals poorly. Signs can build over days rather than minutes. The same applies to a cat sleeping on a pile of stored clothing that smells strongly of mothballs, which is a surprisingly popular cat activity.
Our notes on indoor cat safety in Dunbar and West Side homes cover the wider set of indoor hazards that catch cats out, and the storage areas are the half most people never think about.
What you might notice
Early signs after a pet eats a mothball are usually stomach-related and can look like any other upset:
- Vomiting, often quite soon, and a strong chemical smell to the breath or the vomit.
- Drooling, lip smacking, pawing at the mouth.
- Lethargy, weakness, reluctance to move.
- Loss of appetite.
The signs that mean come in now:
- Tremors, twitching, unsteadiness or a seizure.
- Pale, white or muddy brown gums. This is the one that points to red blood cell damage.
- Dark, brown or red-tinged urine.
- Fast or laboured breathing.
- Yellowing of the gums, the eyes or the skin inside the ears.
- Collapse.
The delay is the dangerous part. With naphthalene, the blood cell damage often shows up a day or two after the event, which is long after an owner has decided the vomiting was a one-off and the pet is over it. That is why we would rather see the animal on the day and take a baseline than hear about it on Wednesday.
What to do if it happens
- Phone us before you do anything else. We can tell you whether this is a come-in-now situation, and with mothballs it usually is.
- Do not make your pet vomit unless we tell you to. Not with salt, not with peroxide, not with anything. Bringing it back up is sometimes exactly right in the first few hours, but it needs to be done here under supervision, and it becomes genuinely dangerous once a pet is unsteady or twitching.
- Give nothing from your own cabinet. Nothing for the stomach, nothing for the nerves, nothing at all.
- Bring the packaging, or a clear photo of the ingredient panel. Which chemical it is changes what we do.
- Count what is missing. How many were in the box, how many are left, and roughly when.
- Get the pet out of the room, then seal the mothballs into a container and take them out before you open the windows. Airing the room does little while the source is still sublimating in it, and this matters most for a cat who has been shut in with the vapour.
- Bring your pet, not just the information. Most of what we need comes from examining them and from bloodwork.
Where the amount or the chemical is a concern, our diagnostics show us what the red blood cells, the liver and the kidneys are doing, which is how we tell whether a pet who looks fine is genuinely unaffected or simply early. A baseline taken on day one is what makes day three readable. Come in through our urgent care and phone on your way so we are expecting you.
Our weekday hours run 8:00 AM to 6:00 PM, Saturday is 10:00 AM to 5:00 PM, and we do not open at all on Sundays or statutory holidays. Saturday morning is the longest gap in our week, since the doors stay shut until ten. At any hour we are closed, take your pet to whichever emergency hospital is open and let them know you are on your way rather than holding on until we unlock.
Doing the storage clear-out safely
None of this means you cannot store wool. It means the box does not live where the dog does.
- Use a sealed container, not a loose box. Mothballs are meant to work inside a closed bin or garment bag with the clothing, where the vapour is contained and no animal can reach the product.
- Never scatter them loose. Not in a crawl space, not in an attic, not under a deck, not in a garden bed, not in a flowerpot. It does not deter wildlife and it does put a dog or cat at risk.
- Sweep the storage areas before you start. Look behind the tank, under the stairs and along the crawl space edges for a product somebody else left. Older houses often have some.
- Bag the old ones properly. Double-bag them and take them to a household hazardous waste drop-off rather than putting them in the kitchen garbage or down the drain.
- Keep the pets out while you work. Shut the door, do the job, vacuum, and air the room before anyone comes back in.
- Air stored clothing outside before it goes back on a bed or a shelf, and especially before a cat sleeps on it.
- Choose something else if you can. Clean clothing stored in sealed containers, and a hard freeze for an infested item, are what actually stop moths. Cedar blocks and dried lavender sachets add a deterrent smell inside a closed container without putting a toxin in the house. Concentrated essential oils, cedarwood and lavender oil included, are a separate problem and should not be applied or diffused around cats.
The rest of the fall storage box
While you are in there, the same cupboards usually hold a few other things worth moving up a shelf. Rodent bait in a crawl space is another common one, and a dog who finds a bait station under a house is a genuine emergency. Old antifreeze and windshield fluid, slug bait left over from the summer, silica gel packets, loose batteries, and half-used bags of fertilizer all belong sealed and high rather than on a basement floor.
Our wellness program visits are a reasonable moment to talk through what is actually in your house, and our medical services team would always rather have that conversation in October than on the phone in a hurry.
Frequently asked questions
My dog ate one mothball and seems completely fine. Do I need to do anything?
Phone us today, and have the box in your hand. One mothball is enough to matter for most dogs, the effects on red blood cells can appear a day or two later, and a pet who looks fine in the first hour tells us very little. A baseline blood sample now is what makes the next few days interpretable.
How can I tell if mine are naphthalene or the other kind?
Read the ingredient panel, which will usually name either naphthalene or paradichlorobenzene, and occasionally camphor, which we would also want to know about. If the box is long gone, assume the more dangerous of the two and tell us that, and we will plan accordingly.
Is the smell alone harmful to my cat?
It can be, with enough exposure in a confined space. A cat who sleeps in a closet with mothballs, or who is shut in a storage room with them, is breathing it in continuously, and cats are poor at clearing these chemicals. If your cat has been shut in or sleeping with that smell, phone us whether or not they look unwell, and straight away if they are lethargic, off their food or breathing oddly.
Can I use mothballs outside to keep raccoons or cats out of my garden?
Please do not. They do not reliably deter anything, they are not approved for that use, they leach into soil, and they put every dog, cat and child who uses that space at risk. There are physical barriers and scent deterrents designed for the job.
Are cedar balls and lavender sachets safe alternatives?
Cedar blocks and dried lavender in a sealed container are a much lower risk and are a reasonable swap. Concentrated essential oils, including cedarwood and lavender oil, are a separate issue and should not be applied or diffused around cats.
What if my dog chewed one and spat it out?
Still phone us first. The mouth absorbs a surprising amount, and the irritation to the lips, gums and tongue is uncomfortable on its own. If your dog is bright and willing you can wipe the mouth or offer water while you are on the phone to us, but do not force water in.
How long should I keep watching after a mothball is eaten?
At least 72 hours, and sometimes longer. We will give you a window based on which chemical it was and how much. The blood cell effects of naphthalene usually build over 24 to 72 hours and can be delayed several days, while brown gums can appear within hours. Dark urine, pale or brown gums, or any yellowing at any point means come straight back.
Speak to the team at Alma Animal Hospital
If your dog or cat has eaten a mothball, or has been shut in with a strong smell of them, phone us with the box in front of you and we will tell you what to do next. Outside our hours, go to the nearest open emergency hospital and call them on the way.
Published by the team at Alma Animal Hospital.
This article is for general educational purposes only and is not a substitute for an in-person veterinary examination or advice about your individual pet. If you have an urgent concern about your pet, contact Alma Animal Hospital or your nearest emergency veterinary hospital right away.
Alma Animal Hospital
3151 Dunbar St, Vancouver, BC V6R 3C2
Phone: (604) 229-5564
Email: reception@almavets.ca
Hours: Monday to Friday 8:00 AM to 6:00 PM; Saturday 10:00 AM to 5:00 PM; Sunday and statutory holidays closed