Summer hazards are well publicised. Everyone knows about hot cars and scorching pavements by July.
Autumn gets almost no attention, and it's arguably the more dangerous season — because the risks are scattered across the ground your dog walks over every day, they look harmless, and several of them kill slowly enough that owners wait too long before calling anyone.
Here's what's actually out there once the leaves start falling.
Antifreeze: The One That Kills Fastest
If you read nothing else here, read this.
Ethylene glycol — the active ingredient in most antifreeze and screen wash — is sweet-tasting, and dogs will drink it voluntarily from a garage floor or driveway puddle. Very small quantities cause fatal kidney failure.
What makes it so lethal is the timeline. The poisoning progresses in stages:
| Stage | Timing | What you see |
|---|---|---|
| 1 | 30 min – 12 hrs | Wobbliness, appearing "drunk", vomiting, excessive thirst and urination |
| 2 | 12 – 24 hrs | Apparent improvement — the dog seems better |
| 3 | 24 – 72 hrs | Kidney failure, collapse, often fatal |
That middle stage is the trap. The dog looks like they're recovering, so the owner decides not to bother the vet. By the time stage three arrives, the window for effective treatment has usually passed.
Treatment exists and works well, but it has to start within hours. Any suspicion of antifreeze exposure is an immediate emergency, symptoms or not.
Practical prevention: store it sealed and elevated, clean up spills completely, check under your car for drips, and be aware that neighbours topping up radiators in autumn is a common exposure route.
Fungi and Wild Mushrooms
Autumn is peak mushroom season, and this is a hazard where owner judgment is essentially useless.
Toxic and harmless species look extremely similar. Even experienced foragers use spore prints and microscopy. There is no reliable field test, and no rule of thumb worth trusting.
Some species — including the death cap, Amanita phalloides — cause a delayed liver failure with the same false-recovery pattern as antifreeze: early gastrointestinal signs, an apparent improvement over 12 to 24 hours, then catastrophic liver damage.
Treat every wild mushroom ingestion as an emergency. If you can safely do so, photograph the mushroom or collect a sample in paper (not plastic) — identification changes treatment.
Check your garden after wet weather and remove anything that appears, especially if you have a dog who eats first and thinks later.
Acorns and Conkers
Acorns contain tannins that cause vomiting, diarrhoea, and abdominal pain. In larger quantities, or with repeated access over weeks, they can cause kidney and liver damage. Green, unripe acorns carry the highest tannin load.
Conkers (horse chestnuts) contain aesculin, producing drooling, vomiting, diarrhoea, and abdominal discomfort.
Both carry a second risk that owners underestimate: intestinal obstruction. Conkers in particular are almost perfectly sized and shaped to lodge in a small or medium dog's gut, and obstruction is a surgical problem, not a wait-and-see one.
Signs of obstruction: repeated vomiting, refusing food, straining without producing anything, a hunched posture, and lethargy. Combined with a hard, distended abdomen, this can also resemble the early presentation of bloat — either way, it warrants urgent veterinary attention.
The practical answer is management: know which trees are on your route, and work on a reliable "leave it" cue. That single behaviour prevents more autumn incidents than anything else.
Blue-Green Algae
Cyanobacteria bloom in still and slow-moving fresh water during warm weather, and blooms frequently persist into early autumn. Some strains produce toxins that cause liver failure or neurological collapse, occasionally within an hour of exposure.
Dogs are exposed by drinking the water, swimming in it, or simply licking their coat afterwards.
What to look for: water with a blue-green, pea-soup, or paint-like appearance; scum or foam along the shoreline; a musty smell. Blooms can also be invisible, which is why local warning signs matter.
Signs of poisoning come on fast — vomiting, diarrhoea, weakness, disorientation, collapse, seizures, difficulty breathing.
There is no antidote. Treatment is supportive and outcomes depend heavily on speed. If your dog has been in water you're unsure about, rinse them thoroughly with clean water immediately and contact your vet.
The simple rule: if you can't see clearly through it, don't let your dog in it.
Rodenticides
Autumn drives rodents indoors, which means more bait being laid — in your home, in neighbours' sheds, in outbuildings and farmland.
The complication for treatment is that different rodenticides work through entirely different mechanisms:
- Anticoagulants prevent blood clotting, with signs appearing 3 to 5 days later — bruising, pale gums, weakness, bleeding
- Cholecalciferol raises calcium to dangerous levels, damaging kidneys
- Bromethalin causes brain swelling and neurological signs
The delayed onset of anticoagulant poisoning means a dog can appear entirely normal for days while the damage accumulates.
Always bring the packaging. The active ingredient determines whether the antidote is vitamin K or something else entirely, and guessing wastes time your dog doesn't have.
Also worth knowing: dogs can be poisoned by eating a rodent that ate bait — secondary poisoning is real.
Fallen Fruit and Garden Debris
Windfall apples, pears, and plums ferment on the ground, and fermenting fruit produces alcohol, to which dogs are far more sensitive than we are. Stones and pits carry both a cyanide risk and an obstruction risk.
Compost heaps deserve particular caution. Decaying organic matter grows moulds that produce tremorgenic mycotoxins, causing tremors, agitation, and seizures. A compost heap is one of the most common overlooked poisoning sources in a garden — fence it off.
Several autumn plants and bulbs are also toxic, and this is a good moment to revisit what's safe generally — our complete guide to foods dogs can and can't eat covers the kitchen side of the same problem.
The Less Dramatic Autumn Risks
Parasites don't stop. Ticks stay active through mild autumn weather, and fleas thrive in centrally heated homes all winter. Stopping preventatives in September is a common and entirely avoidable mistake. Harvest mites peak in late summer and autumn, causing intense irritation between the toes and around the ears.
Darker walks. Reflective gear or a light-up collar for both of you, and a reminder that a dark dog on an unlit road is effectively invisible to drivers.
Cold and damp affect arthritic dogs. Older dogs stiffen noticeably as temperatures drop. Keep beds away from draughts, maintain gentle consistent movement rather than stopping walks, and speak to your vet if mobility worsens — our senior dog care guide covers the joint side in depth.
Fireworks season begins. Preparation needs a long lead time, which is covered properly in our noise phobia guide.
Coat, Paws and the Wet-Weather Routine
Autumn is hard on coats and feet, and the resulting problems are the ones that quietly turn into vet visits.
Grass seeds and burrs remain a genuine hazard into early autumn. Grass awns are barbed and travel in one direction only — they burrow into skin, between toes, into ears, and occasionally migrate a long way internally. Check between the toes, under the armpits, and inside the ear flaps after every walk through long grass. A dog suddenly shaking their head, tilting it, or obsessively licking one foot needs looking at properly.
Mud and moisture create the conditions for skin problems. Dry your dog properly after wet walks, paying particular attention to the spaces between the toes and the skin folds of wrinkled breeds. Damp trapped against skin is how hot spots and yeast infections start.
Road salt and grit appear as soon as the first frosts arrive. Both irritate paw pads and are unpleasant if licked off. Rinse paws after walks once gritting starts.
Cracked pads become more common as humidity drops and surfaces get harsher. Check pads weekly for splits, and see your vet for anything deep or bleeding rather than treating it at home.
The Autumn Emergency Checklist
Symptoms that mean call your vet now, not tomorrow:
- Wobbliness or appearing drunk
- Repeated vomiting, or vomiting with lethargy
- Refusing food combined with a hard or distended abdomen
- Pale, white, or bluish gums
- Tremors, twitching, or seizures
- Unexplained bruising or bleeding
- Collapse or extreme weakness
- Straining to pass stool with nothing produced
When you call, have ready: your dog's current weight, what they may have eaten, roughly how much, when, and any packaging or a photo.
Weight matters more than owners expect — nearly all toxicity is calculated per kilogram, and "about twenty kilos, I think?" is a materially worse starting point than a figure from last week.
Keep the Details Where You Can Find Them
PawDex keeps weight history, medication schedules, and daily notes in one place, ready to export for a vet visit. In a poisoning call, being able to give an exact current weight and confirm what medication your dog is on changes the advice you get.
Download PawDex free on Google Play, or browse more seasonal safety guides on the PawDex blog.
Most of this season's incidents are prevented by two things: knowing what's on your walking route, and a dog who will genuinely leave something when asked. Both are worth the effort now, before the leaves come down.
This article is educational and does not replace veterinary care. If you suspect your dog has ingested any toxin, contact your veterinarian or an emergency animal poison control service immediately — do not wait for symptoms to appear.
Frequently Asked Questions
Yes. Acorns contain tannins that cause vomiting, diarrhoea, and in larger quantities kidney and liver damage. They are also a common cause of intestinal obstruction, particularly in smaller dogs.
Treat it as an emergency and call your vet immediately. Toxic species cannot be reliably distinguished from safe ones by appearance, and some cause fatal liver failure after symptoms appear to improve.
Extremely. Ethylene glycol tastes sweet and very small amounts cause fatal kidney failure. Treatment must begin within hours to work, so any suspected exposure is an immediate emergency.
Blue-green algae are cyanobacteria that bloom in still water during warm weather and can persist into autumn. Some produce toxins that cause rapid liver failure or neurological collapse, sometimes within an hour.
Yes. Horse chestnuts contain aesculin, which causes vomiting, diarrhoea, and drooling. Their size and shape also make them a serious choking and intestinal obstruction risk.
Yes. Ticks remain active in mild autumn weather and fleas thrive in heated homes through winter. Stopping preventatives in September is a common and avoidable mistake.