Allergic reaction in dogs

Recognise the signs

• MILD TO MODERATE: Hives (urticaria) — raised bumps appearing under the fur, often visible on belly, face, or inner legs
• Facial swelling — puffiness around the eyes, muzzle, or lips (angioedema)
• Redness and itching — dog pawing at face, rubbing muzzle on the ground
• Watery eyes and runny nose
• Vomiting — single episode without other severe signs
• SEVERE (ANAPHYLAXIS): Sudden profound weakness or collapse
• Extreme pallor of gums — white or grey mucous membranes
• Rapid, weak, or thready pulse
• Difficulty breathing, gasping, or wheezing
• Uncontrolled vomiting or diarrhoea
• Loss of bladder or bowel control
• Loss of consciousness

First aid steps

1. 1. Assess the severity immediately. Can the dog stand? Is it breathing normally? What colour are the gums?
2. 2. If ANAPHYLAXIS suspected (collapse, pale gums, breathing difficulty): phone emergency vet NOW. Drive immediately — do not wait for the vet to call back.
3. 3. If MILD (hives, swelling, itching, alert dog, pink gums): phone your vet for same-day advice. Remove the dog from the source of the allergen if known.
4. 4. If a bee sting is visible: remove the sting by scraping it sideways with a firm card (e.g., bank card) — do not squeeze it as this injects more venom. Apply a cool compress to the sting site.
5. 5. If a wasp sting: no sting left behind. Apply a cool compress to reduce swelling.
6. 6. Do not give antihistamines without veterinary guidance — they are rarely sufficient for serious reactions and may mask deterioration.
7. 7. Keep the dog warm and calm. Lay a mildly unwell dog on their side if they seem faint.
8. 8. Monitor gum colour every few minutes during transit — pale or blue gums mean deterioration; increase urgency.

While transporting to the vet

• Keep the dog lying quietly — do not let an anaphylactic dog exert itself.
• Keep the dog warm with a blanket.
• Monitor breathing rate and gum colour continuously.
• Phone ahead so the vet can prepare adrenaline (epinephrine) and IV access.
• If the dog stops breathing and has no pulse: only attempt CPR if trained to do so.

When it can usually wait

• Very mild hives affecting only a small skin area, dog is alert, eating and drinking, gums are pink — phone vet for advice but may not need emergency appointment.
• Minor itching or redness following contact with nettles or grass with no swelling of the face.

Common causes

• Insect stings — bee and wasp stings are the most common trigger in the UK; dogs often investigated with nose or paws
• Vaccine reactions — can occur within 20–30 minutes of vaccination; most common with inactivated (killed) vaccines
• Drug reactions — antibiotics (especially penicillins), NSAIDs, or anaesthetic agents
• Food — certain proteins (beef, chicken, dairy, egg) can occasionally trigger acute reactions, though chronic food allergy is more common
• Topical products — shampoos, flea treatments, or household chemical contact
• Snake bite — adder (Vipera berus) is the UK's only venomous snake; causes local swelling and systemic reaction
• Environmental allergens — grass pollen, dust mites (more commonly cause chronic atopy)
• Contact allergens — plants, nettles, or materials the dog has rolled in

What the vet will need to know

• What do you think caused the reaction and when did it start?
• Has the dog been vaccinated or received any medication today?
• Was the dog stung? Where on the body and when?
• What signs are present and how quickly did they develop?
• Gum colour now?
• Is the dog conscious and standing?
• Any previous allergic reactions?
• Current medications or flea/worm treatments?

Aftercare

• The vet will typically administer adrenaline (epinephrine) for anaphylaxis, antihistamines, and corticosteroids, and may give IV fluids.
• Dogs treated for anaphylaxis are usually monitored at the practice for several hours — biphasic reactions (a second wave of anaphylaxis hours later) can occur.
• The vet may prescribe a short course of antihistamines or steroids following a mild reaction.
• Discuss with your vet whether an emergency adrenaline kit is appropriate for dogs with a known severe allergy history.
• Avoid identified allergen sources in future — if it was a bee sting, be vigilant near flowering plants and food in summer.
• Consider allergy testing if the cause is unclear and reactions are recurrent.

Prevention

• Avoid known allergen sources where possible.
• If your dog has had a vaccine reaction previously, inform the vet before every future vaccination — the dog should be pre-medicated and observed for at least 30 minutes post-injection.
• Walk dogs away from areas with heavy bee or wasp activity in summer.
• Do not leave dogs unattended near food that could attract stinging insects.
• Carry your vet's emergency number on your phone at all times.
• Dogs with a known history of severe reactions may benefit from a vet-prescribed emergency antihistamine dose to keep at home — discuss this with your vet.

Breed-specific notes

• No specific breed is immune, but Boxers, Labrador Retrievers, and Golden Retrievers appear to be overrepresented for atopic allergies.
• Brachycephalic breeds (French Bulldog, Pug, Bulldog) — facial swelling from allergic reactions can more rapidly compromise their already narrow airways.
• Large and giant breeds may present with different signs of anaphylaxis, including bloating and cardiovascular collapse.

Frequently asked questions

Related topics

• Dog stung by a bee or wasp
• Food allergy or intolerance in dogs