Dog vomiting or unwell after vaccination

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

1. Mild signs: rest, monitor, contact vet if not improving in 24–48 hours.
2. Allergic signs: phone the vet today.
3. Anaphylaxis: drive to the vet now (see pet-allergic-reaction-acute).

While transporting to the vet

• For severe reactions, drive without delay.

When it can usually wait

• 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

Related topics

• Acute allergic reaction (anaphylaxis) in dogs and cats