Urgent — same day vet contact
Immediate for severe reaction; same day for moderate
Dog vomiting or unwell after vaccination
Mild dullness 24 hours after vaccination is common; vomiting, facial swelling, hives, breathing difficulty, or collapse is allergic reaction — phone the vet today.
Recognise the signs
- Mild: dullness, low appetite, tender at injection site, mild fever — usually 24-48 hours
- Allergic: facial swelling, hives, vomiting, diarrhoea — within hours
- Anaphylaxis: collapse, breathing difficulty, pale gums — minutes
First aid steps
- Mild signs: rest, monitor, contact vet if not improving in 24–48 hours.
- Allergic signs: phone the vet today.
- Anaphylaxis: drive to the vet now (see pet-allergic-reaction-acute).
Do NOT
- Do not give human antihistamines without vet advice.
- Do not assume vaccine reactions don't happen — they do, particularly in small breeds.
While transporting to the vet
- For severe reactions, drive without delay.
When to phone the vet immediately
- Facial or muzzle swelling
- Hives, persistent vomiting
- Breathing difficulty, collapse
Signs that can usually wait for a routine appointment
- Mild dullness without other signs in the first 24 hours of vaccination usually resolves.
Common causes
- Mild post-vaccine immune response (normal, common)
- Allergic reaction (uncommon but possible)
- Anaphylaxis (rare but emergency)
What the vet will need to know
- Vaccines given and time
- Onset of signs
- Severity
Aftercare
- Severe reactions noted in records — future vaccines may be split or pre-medicated.
- Discuss vaccine schedule and necessity for individual dog.
Prevention
- Brief vet about previous reactions.
- Watch for 1–2 hours after vaccination at the practice if previous reaction.
- Some dogs benefit from antihistamine premedication on vet's advice.
Breed-specific notes
- Slightly higher reaction rates: small breeds, especially Dachshund, Boston Terrier, Chihuahua.
Frequently asked questions
Should I skip vaccines if my dog reacted?
Discuss with the vet — most dogs can be re-vaccinated with adjustments. Some may have non-essential vaccines omitted.
How long do mild post-vaccine signs last?
Usually 24–48 hours. Beyond that, contact the vet.
Can I premedicate next time?
Some vets prescribe antihistamine before known reactor visits. Don't self-medicate.