A Common Garden Product With Deadly Consequences
Slug pellets are one of the most frequently used pesticides in UK gardens. They are cheap, widely available, and effective at controlling the slugs and snails that damage plants. They are also one of the most common causes of serious and fatal poisoning in dogs, and the risk is significant enough that the UK government restricted the use of metaldehyde-based products for amateur gardeners in 2022. Despite this, stocks remain in circulation and the compounds are still in use by farmers and some professional applications, meaning exposure risk has not disappeared.
Metaldehyde poisoning is fast-moving and brutal. It is not a situation that improves with a wait-and-see approach. Understanding why these products are so dangerous, what the signs look like, and how quickly treatment must begin is essential for anyone with dogs who spends time in or near gardens.
What Metaldehyde Does in the Body
Metaldehyde is a polymer of acetaldehyde that, when ingested, breaks down and disrupts normal neurological function. The precise mechanism is not fully understood, but it is known to deplete inhibitory neurotransmitters in the central nervous system, leading to uncontrolled excitatory activity in the brain and throughout the nervous system.
The result is severe and progressive neurological dysfunction. Dogs are attracted to slug pellets because many products contain attractants such as bran or molasses intended to draw slugs to the bait. These same attractants make the pellets appealing to dogs, who may eat large quantities very quickly.
There is no antidote to metaldehyde. Treatment is entirely supportive, focused on controlling the neurological signs and keeping the dog alive while the toxin is metabolised. This is why speed of presentation to a vet is so critical.
The Timeline of Metaldehyde Toxicity
The speed with which metaldehyde causes symptoms is one of the things that makes it so dangerous. Signs can begin within thirty minutes to three hours of ingestion, and they escalate rapidly.
- Early phase (within one to two hours): anxiety, restlessness, excessive salivation, vomiting, twitching of facial muscles
- Progressive phase: generalised muscle tremors that become increasingly severe, incoordination, hyperthermia as the constant muscle activity generates body heat
- Severe phase: continuous seizures (status epilepticus), hyperthermia reaching dangerous levels, respiratory distress, metabolic acidosis
- Without treatment: death from respiratory failure, hyperthermia, or severe metabolic disruption
The hyperthermia that develops as a secondary consequence of the constant muscular activity can itself cause irreversible organ damage, including brain damage, very quickly. Dogs with severe tremors or seizures can reach body temperatures above 41 degrees Celsius within a short period, which adds another life-threatening layer to the primary neurological toxicity.
How Much Is Dangerous
Metaldehyde has a relatively low toxic dose in dogs. The lethal dose in dogs is estimated at around 100 to 1000 mg per kilogram of body weight, but signs of toxicity can appear at doses well below this. Traditional slug pellet formulations typically contain around 3 to 6 percent metaldehyde, but higher concentration products exist.
A small dog that consumes a meaningful quantity of pellets, which can happen in seconds given the attractant formulations used, may have ingested a potentially lethal dose before the owner is even aware of what has happened.
What to Do If You Suspect Ingestion
This is a situation requiring immediate action, not observation. Do not wait for symptoms. Do not call a non-emergency line and wait for a callback. Go directly to a vet or emergency veterinary service.
- If you see your dog eating slug pellets, call a vet immediately while making your way there
- If symptoms such as tremors or seizures have already begun, treat this as a critical emergency
- Take the product packaging with you so the vet can confirm the active ingredient and concentration
- Do not attempt to induce vomiting at home, particularly if neurological signs are already present, as this can increase the risk of aspiration
The vet will focus on decontamination if the ingestion was very recent and the dog is not yet showing signs. Once neurological symptoms are present, the priority shifts to controlling tremors and seizures with medications such as diazepam or methocarbamol, reducing body temperature, supporting hydration and organ function, and preventing aspiration.
Preventing Exposure
The restriction on metaldehyde products for amateur use in the UK brought alternative active ingredients, particularly ferric phosphate (iron phosphate), into mainstream availability. Ferric phosphate-based slug pellets are considered significantly safer for pets and wildlife, though they are not entirely without risk in large quantities.
- Switch to ferric phosphate-based slug control products if you use pellets in a garden accessible to dogs
- Store all slug pellets and pesticides in locked or secured storage inaccessible to pets
- If using pellets in any area, apply them under boards or tiles that slugs can access but dogs cannot, rather than scattering them openly
- Be aware that neighbouring gardens, allotments, and agricultural land may still use metaldehyde formulations
- Keep dogs on leads or under direct supervision when walking near farmland, particularly during wetter months when slug control is more commonly applied
It is also worth noting that cats can be affected by metaldehyde, though they are less commonly poisoned because they tend to be less indiscriminate in what they eat. The same precautions apply.
Recognition Saves Lives
Metaldehyde poisoning is survivable with rapid and aggressive veterinary treatment. Dogs that reach a vet quickly, before severe hyperthermia or prolonged seizures have caused secondary damage, have a reasonable chance of recovery. Dogs that are brought in late, after extended periods of uncontrolled tremors, face a much more guarded prognosis.
The single most important factor in outcome is time. Any dog owner who knows that their dog has eaten, or may have eaten, slug pellets should treat the situation as an emergency from the first moment of suspicion. An unnecessary vet visit is a small inconvenience. A delayed one can be irreversible.