Yellowjacket colonies reach their largest size in September and October, and the workers turn to scavenging just as dogs spend more time in the yard. Most stings cause a sore, puffy spot that settles within a day. A sting inside the mouth, many stings at once, or a pet who vomits or collapses is an emergency.
Why early fall is sting season
A yellowjacket nest starts in spring with a single queen and grows all summer. By September it can hold thousands of workers, and the colony’s food needs change. Instead of hunting insects, workers go looking for protein and sugar: meat scraps, pet food, fallen fruit, open soda cans and anything sweet left outside.
That puts them exactly where pets are. A bowl of kibble on the patio, a fig or plum dropping into the grass, a barbecue on a warm October evening. Palo Alto often gets warm spells in September and October, so the yard stays busy with both people and wasps well into the season.
The western yellowjacket usually nests in the ground, often in an old rodent burrow. The only sign may be a small hole with a steady stream of wasps flying in and out. A dog who digs at that hole, or a cat who lies down beside it, can set off a defensive swarm.
How dogs and cats get stung
- Snapping at them. Many dogs see a buzzing wasp as a game, which leads to stings on the lips, tongue and inside the mouth.
- Digging. Terriers and other enthusiastic diggers can open a ground nest and take dozens of stings in seconds.
- Stepping on one. Yellowjackets feeding on fallen fruit are easy to tread on, giving stings to the paw pads.
- Food bowls outside. A wasp crawling on kibble can end up in a mouthful of dinner.
- Cats hunting. Cats bat at flying insects and are usually stung on the paws or face.
Unlike honeybees, yellowjackets do not leave a stinger behind and can sting repeatedly. If you find a stinger with a small sac attached, that was a bee.
A normal sting versus an emergency
It helps to think of reactions in three levels.
Local reaction: usually fine at home
A single sting on a leg, paw or body causes a small swollen, tender spot. Your pet may lick it, limp for a while or seem a bit sorry for themselves. This usually settles within a day.
Larger reaction: phone us now
A swollen face or muzzle, puffy eyelids, or raised bumps (hives) across the body mean the immune system is reacting more strongly. These pets often look dramatic but stay bright. They still need to be seen right away, because a larger reaction can progress, so if we are closed, make for the closest open emergency hospital.
Emergency: come in now
- Any sting inside the mouth or throat, or swelling around the neck
- Noisy, labored or fast breathing
- Vomiting or diarrhea soon after a sting
- Pale gums, weakness, wobbliness or collapse
- More than a handful of stings at once, particularly in a small dog or a cat
In dogs, a severe allergic reaction often shows up in the gut first, with sudden vomiting or diarrhea within minutes of the sting, followed by weakness. Many owners do not connect that to the wasp in the yard ten minutes earlier. If your dog has been anywhere near yellowjackets and suddenly vomits and seems listless, phone our urgent care team right away. After we close, head for the nearest open emergency hospital and call ahead from the car.
What to do in the first ten minutes
- Move away from the nest. Walk your pet calmly indoors or to another part of the yard. More wasps will follow a disturbance.
- Look at the mouth and face. If there is swelling inside the mouth or any effort in the breathing, put this down and leave now for the clinic, or for an open emergency hospital after hours.
- Check for a stinger. If there is one, remove it as fast as you can, by whatever method works. Speed matters more than technique.
- Cool the spot. A cloth wrapped around an ice pack, held on for a few minutes at a time, eases swelling on a leg or paw.
- Do not give anything from your own cabinet. Something that suits a person can harm a dog or cat, and the amount matters. Let us decide what is appropriate.
- Watch closely for the first few hours, then keep an eye on your pet for the rest of the day. Most serious reactions appear quickly, but some build more slowly.
If your pet had a big reaction once, tell us. Future stings can cause a stronger reaction, and our medical services team can help you plan ahead for next season.
Cutting sting risk around the house
- Feed pets indoors through October, and pick up bowls rather than leaving food out.
- Collect fallen fruit every day. Fermenting fruit attracts yellowjackets in large numbers.
- Keep lids on trash and recycling bins, and rinse soda and juice cans before they go out.
- Walk the yard once a week looking for a small hole with wasps flying in and out, especially near fences and under shrubs. Keep pets away from it.
- Have ground nests removed by a professional, ideally in the evening when workers are inside. Do not try to flood or dig out a nest yourself.
- Discourage wasp games. Call your dog away and reward them when they leave a buzzing insect alone.
Yellowjackets are one of several fall hazards hiding in Palo Alto yards. Our guide to toxic garden plants in Palo Alto covers the ones that grow rather than fly.
Frequently asked questions
A sting on the paw has left my dog limping. Does that need a visit?
Usually not, if it is a single sting on the leg or paw and your dog is otherwise bright, breathing normally and not vomiting. Cool the spot and watch. Phone us if the swelling spreads, the face starts to puff up, or your dog is still very sore the next day.
How fast does a serious reaction happen?
Often within minutes, and most show up within the first hour. Facial swelling and hives can take a little longer. If anything beyond a small local bump appears, phone us rather than waiting to see where it goes.
My dog ate a yellowjacket. Is that dangerous?
It can be. The concern is a sting inside the mouth or throat, where swelling can affect breathing. Look inside the mouth, watch for drooling, pawing at the face or noisy breathing, and come in right away if you see any of them.
Can cats have a severe reaction too?
Yes, although they tend to be stung less often. Breathing trouble is the most important warning sign in a cat, and drooling, a swollen face or weakness after a sting also mean phoning us right away. Cats are good at concealing how uncomfortable they feel, so err on the side of calling.
What about many stings at once?
It is an emergency, even without an allergy. A dog who disturbs a ground nest can be stung dozens of times, and that many stings is harmful on its own, particularly for small pets. Move your pet well away from the nest, then come right in.
My pet reacted badly to a sting before. What should I do now?
Book a visit with our pet care services team to talk it through before the next sting. Later reactions can be stronger, and we can make a plan that fits your pet, including exactly when to come in right away.
Speak to the team at Universal Pet Hospital
If your pet has been stung and has a swollen face, trouble breathing, or is vomiting, phone us now, or go to the nearest open emergency hospital if we are closed.
Published by the team at Universal Pet Hospital.
This article is for general educational purposes only and is not a substitute for an in-person veterinary examination or advice about your individual pet. If you have an urgent concern about your pet, contact Universal Pet Hospital or your nearest emergency veterinary hospital right away.
Universal Pet Hospital
3337 El Camino Real, Palo Alto, CA 94306
Phone: (650) 362-7969
Hours: Monday to Friday 8:00 AM to 7:00 PM; Saturday and Sunday 9:00 AM to 5:30 PM