Compost & Mould Poisoning in Pets UK — Mycotoxins Emergency Guide

According to the BVA and Animal PoisonLine, mycotoxins are poisonous chemicals produced by fungi growing on decaying organic matter. Compost heaps, food waste bins, and mouldy leftovers are ideal environments for toxin-producing moulds.

UK pets are poisoned when they:

• Raid kitchen compost caddies or outdoor compost bins
• Eat mouldy bread, pasta, rice, or nuts from counters or bins
• Scavenge mouldy food dropped at barbecues, picnics, or bird tables
• Dig into garden compost heaps or leaf mould piles
• Eat mouldy windfall fruit or fermented vegetation in autumn

Dogs are the most common victims due to scavenging behaviour. Cats accessing indoor caddies or outdoor bins are also at risk.

The most dangerous compost-related toxins in UK pets are tremorgenic mycotoxins — including roquefortine C and penitrem A from certain mould species.

These toxins attack the nervous system, causing:

• Muscle tremors — fine shaking to violent jerking
• Rigidity and hyperthermia (high temperature)
• Seizures
• Collapse and death in severe cases

Tremorgenic poisoning can progress rapidly — from mild tremors to seizures within hours. Early veterinary treatment is essential.

Other mycotoxins cause primarily liver damage — similar to some mushroom poisons — with vomiting, jaundice, and bleeding. Aflatoxins from mouldy nuts and grains target the liver.

Signs typically appear within 30 minutes to a few hours after ingestion:

Some dogs show ataxia — wobbling and inability to walk normally — before tremors become obvious.

Do not assume mild tremors will pass without treatment. Toxins can escalate to life-threatening seizures.

According to the PDSA and RSPCA, typical cases involve:

• Kitchen compost caddies left open on worktops — dogs and cats pull out mouldy tea bags, bread, and pasta
• Garden compost bins with loose lids — dogs knock them over in gardens
• Autumn windfall apples fermenting on lawns — alcohol and mould together worsen toxicity
• Bird table scraps and mouldy fat balls
• Bin raiding on collection day — mouldy food waste in wheelie bins
• Forgotten lunchbox contents in children's bags or cars

Autumn and warm wet weather increase mould growth — risk peaks when compost heaps are damp and warm inside.

Compost poisoning is distinct from:

• Slug pellets (metaldehyde) — causes rapid tremors and seizures too — see slug pellet poisoning
• Onion and garlic in food waste — causes delayed anaemia — see onion and garlic poisoning
• Grapes and raisins in discarded baking — kidney failure — see grape poisoning in dogs
• Xylitol in sugar-free gum thrown in bins — see xylitol poisoning in dogs

Food waste often contains multiple hazards — mould toxins plus toxic foods. Treat any compost or bin scavenging as potentially serious.

According to Blue Cross and PDSA guidance:

Kitchen

• Use sealed compost caddies — never leave open on counters
• Empty caddies frequently into outdoor bins
• Keep caddies in closed cupboards or behind child-proof latches if pets counter-surf
• Dispose of mouldy food in outdoor wheelie bins with secure lids — not indoor bins pets can open

Garden

• Use closed compost bins with locking lids — not open heaps if you have dogs
• Fence off traditional compost heaps and leaf mould piles
• Clear windfall fruit from lawns regularly in autumn
• Secure wheelie bins — store behind gates if dogs raid bins
• Clean barbecue and picnic areas immediately after eating

Training and walks

• Teach strong "leave it" for scavenging on walks
• Supervise dogs in gardens — compost bins tip when dogs lean on them
• Avoid letting dogs dig in leaf piles where mould develops

For mouldy vegetables in the fridge — throw in outdoor bin, not open compost accessible to pets.

Some owners believe dogs can eat stale bread or mouldy cheese because "dogs eat anything." This is dangerous. Never feed mouldy food intentionally.

Mould on cheese, bread, nuts, and grain products carries tremorgenic and liver toxins. If you would not eat it, your pet should not either.

Safe vegetable scraps without mould are a separate topic — see what vegetables can dogs eat UK. Mouldy versions are toxic.