Processionary Caterpillars & Dogs in Spain: Emergency Steps

If your dog has just touched a processionary caterpillar, stop reading and act: do not rub the mouth, rinse it gently with lukewarm water, and drive to the nearest vet immediately. This is a genuine emergency where minutes decide whether your dog keeps its tongue — and its life. The rest of this guide explains why, what symptoms to watch, and how to make sure it never happens again.

The pine processionary caterpillar (Thaumetopoea pityocampa) is the single most dangerous pest to dogs in Spain. Every spring, Spanish vets treat thousands of poisoning cases — and expats walking dogs near the pretty pine woods of the Costa del Sol, the Balearics, or inland Andalucía are often caught completely unaware.

Why Are Processionary Caterpillars So Dangerous to Dogs?

The danger is not a bite or a sting — it’s the caterpillar’s defence system. Each caterpillar is covered in an estimated 500,000+ microscopic barbed hairs. When threatened, disturbed, or touched, it fires these hairs into the air and into whatever contacts it. The hairs carry a protein toxin called thaumetopoein, which triggers an immediate, aggressive inflammatory reaction.

Dogs are the perfect victims because they explore the world with their nose and mouth — the exact behaviours that release and embed the hairs. A dog that sniffs a procession on a path, or worse, licks or bites a caterpillar, gets a mouthful of toxin-loaded barbs.

Symptoms of Processionary Caterpillar Poisoning in Dogs

Learn these signs. They appear in roughly this order, often within 5–30 minutes of contact:

• Sudden, heavy drooling (hypersalivation) — often the very first sign
• Pawing at the mouth, distress, and restlessness
• Swollen tongue and lips — the tongue may look visibly enlarged
• Discolouration of the tongue — going pale, bluish, or black in patches (necrosis)
• Vomiting and loss of appetite
• Fever and lethargy
• Difficulty breathing or swallowing if the throat is affected

What To Do: The First 10 Minutes (Step by Step)

1. Stay calm and protect yourself. The hairs affect humans too. If you handle your dog’s mouth, avoid touching your own eyes and wash your hands afterwards. Wear gloves if you have them.
2. Do NOT rub, scrub, or wipe the mouth. Rubbing drives the barbed hairs deeper into the tissue and spreads them. This is the most common — and most damaging — mistake.
3. Rinse gently with lukewarm water. Pour water repeatedly over and into the mouth and tongue, letting it run straight out. Do not let your dog swallow it. Warm water is preferred over cold because the toxin is temperature-sensitive. Keep rinsing for a few minutes.
4. Call ahead and go to the vet immediately. Phone your vet or the nearest 24-hour emergency clinic so they can prepare, then drive there. Bring a photo of the caterpillar or nest if you can do so safely.
5. Do not give food, milk, or home remedies. They don’t neutralise the toxin and can delay professional care.

When and Where Is the Risk Highest in Spain?

The pine processionary follows a predictable calendar, and the ground phase is the dangerous one:

• January–April: peak risk. Caterpillars descend from their nests and form processions on the ground, in gardens, on paths, and across roads — right where dogs walk.
• Warm winters: processions can appear as early as December or January, especially on the southern coast.
• Summer and autumn: low direct risk from processions, but nests are forming high in the pines, ready for next season.

Risk exists anywhere pine trees grow, which is most of the country: the Costa del Sol and inland Andalucía, the Costa Blanca, Madrid’s pine belts, Catalonia, and across Mallorca, Ibiza, and the Canary Islands. Our month-by-month seasonal pest calendar shows exactly when to be on alert in your region.

How To Protect Your Dog — Prevention That Works

Prevention is far better than any emergency response. Combine these:

• Lead and awareness. Keep dogs on a short lead near pines from January to April. Scan the ground before letting your dog sniff. Never let a dog approach a “line” of caterpillars — that fascinating procession is the threat.
• Train a rock-solid “leave it.” A reliable recall and leave-it command has saved many dogs’ lives.
• Spot the nests. Processionary nests are unmistakable white silken “cotton ball” cocoons hanging in the tips of pine branches. If you see them on or near your property, plan treatment before winter’s end.
• Treat your own trees early. Pheromone traps and physical trunk-collar barriers stop caterpillars before they reach the ground. Fit trunk barriers in late winter, and set pheromone traps from summer to catch the male moths. For infested pines, professional nest removal is the safest option — see our complete processionary guide.
• Report processions. Most Spanish ayuntamientos have a free line or online form to report processions in public areas so the council can treat or barrier the trees.
• Carry water. A bottle of water in your walking bag means you can start rinsing within seconds of contact — the difference between a scare and a tragedy.

What About Cats, Children, and Adults?

Cats are even more sensitive than dogs relative to their size — a single caterpillar can be fatal — but they contact them less often because they investigate with paws rather than mouths. The same emergency steps apply.

Children are the most at-risk humans, because they may pick up or poke the caterpillars. Contact causes urticaria (hives), intense itching, and painful welts on skin; eye contact causes conjunctivitis; and inhaled hairs can trigger asthma-like symptoms. Teach children never to touch caterpillars, and rinse skin (don’t scratch) if contact happens.

Adults usually get off with a skin rash, but gardeners and hikers should avoid disturbing nests, especially on windy days when airborne hairs travel.

The Bottom Line

The pine processionary caterpillar turns an ordinary spring dog walk into a potential emergency. But it is entirely manageable if you know the season, keep your dog on a lead near pines, act within minutes if contact happens, and treat the trees on your own property before the caterpillars descend.

Two things to do right now: save your nearest 24-hour vet’s number, and read our complete pine processionary caterpillar guide so you can identify nests and processions before your dog does. For the wider picture of keeping pets safe, see our guide to pet-safe pest control in Spain and our tick season guide — the other spring hazard for Spanish dogs.