Photograph: Unsplash (free licence).
Quick answer: the pine processionary caterpillar has stinging hairs that can cause serious injuries to a dog’s mouth and tongue. The caterpillars usually come down from the pines from mid or late January, and in 2026 veterinary associations warned that the season had started early in several areas. This winter: keep your dog on a lead in pine woods, do not let them sniff or touch the caterpillars and, if there is contact, rinse without rubbing and go straight to the vet.
Although it is still autumn, now is a good time to prepare. The white silky nests you see high in pine trees belong to the processionary caterpillar, and in a few weeks the caterpillars will start coming down to the ground in single file to bury themselves.
What happened last season
On 29 January 2026, the Alicante College of Veterinary Surgeons (Icoval) warned that the season may have started slightly early and that it had received a good number of cases of varying severity, all linked to walks in pine woods. In mid-February, Anecpla, the Spanish association of environmental health companies, reported that the pest had also been detected in Murcia and Castellón and was expected in other parts of Spain.
According to Icoval, the caterpillars’ descent lasts almost a month and is the period of greatest risk for dogs. Each caterpillar has around 500,000 stinging hairs, according to Anecpla.
Symptoms in dogs
Contact from sniffing, licking or biting a caterpillar can cause:
- Swelling of the tongue, lips or muzzle.
- Excessive drooling, itching and vomiting.
- Mouth ulcers and eye injuries.
- In severe cases, tongue necrosis, breathing problems or a serious allergic reaction.
It is a veterinary emergency: the sooner it is treated, the better the outlook.
What to do if your dog touches a processionary caterpillar
- Protect your hands with gloves so you do not touch the hairs.
- Rinse the area without rubbing (mouth, lips, tongue, muzzle or paws) with saline solution or water with bicarbonate of soda, as Icoval recommends.
- Go to the vet straight away, even if the symptoms seem mild.
- Do not try to remove caterpillars or nests yourself: report them to your local council or a specialist company.
Prevention on winter walks
- Use a lead in pine woods and parks with pine trees during the weeks when the caterpillars come down in your area.
- Watch the ground: lines of caterpillars are easy to spot if you pay attention.
- Choose routes without pines in the riskiest weeks and make up for it with sniffing games at home.
- Check your garden: if you have pine trees, ask a professional for advice before the caterpillars come down.
See more dog leads, collars and harnesses and dog wipes.
Frequently asked questions
When is the risk highest?
When the caterpillars come down from the pines to the ground, usually from mid or late January and for almost a month. In warmer areas it can start earlier, so it pays to stay alert from the start of winter.
Are cats at risk too?
Yes, any animal that touches the caterpillars can be injured, although dogs are most affected because they sniff and bite what they find on the ground.
Can I give my dog anything at home?
Do not give them any medication on your own initiative. Rinse the area without rubbing and call or go to the vet immediately.
Keep reading
- Sniffing games for dogs: easy ideas at home
- How to measure your dog and choose a harness size
- Walking your dog in the rain: a practical checklist