Your puppy just got their shots, and now they’re acting… off. Maybe they’re sleeping more than usual, ignoring their food bowl, or you’ve noticed a weird little bump where the needle went in. I get it — the panic sets in fast.
Here’s the thing. Most puppy vaccine side effects are completely normal and clear up within a day or two. I’ve been through this with every dog I’ve owned over the past 15+ years, from my Golden Retrievers to my Border Collies, and I still get that little knot in my stomach every time. But knowing what’s normal versus what actually warrants a frantic call to your vet? That makes all the difference.
So let’s break down exactly what to expect after your puppy’s vaccinations — the stuff that’s fine, the stuff that needs attention, and everything in between.
Normal Side Effects After Puppy Vaccinations
Most puppies sail through their shots with barely a whimper. But vaccines work by triggering an immune response, so your puppy’s body is literally learning to fight off diseases. That takes energy. And sometimes it shows.
The vast majority of side effects fall into the “totally expected” category. Think of it like how you feel after a flu shot — a bit run-down, maybe a sore arm. Your puppy’s version of that looks like this.
Mild Lethargy and Reduced Appetite (12-24 Hours)
This is the big one. If your puppy is lethargic after vaccination, you’re not alone in worrying — but it’s the single most common reaction I see new owners stress about.
Your normally bouncy puppy might:
- Sleep significantly more than usual
- Show zero interest in their food bowl
- Seem “flat” or subdued
- Not want to play or go for walks
This is completely normal and typically resolves within 12 to 24 hours. Some puppies bounce back in as little as 6 hours. My Border Collie, who normally has the energy of a small tornado, once slept for nearly 18 hours straight after her 12-week shots. By the next morning she was stealing socks again.
If your puppy’s not eating after shots, don’t force it. Offer their regular food, make sure fresh water is available, and let them rest. Most puppies will eat again by the next meal. If they skip two full meals (roughly 24 hours for puppies fed twice daily), that’s when I’d start paying closer attention.
One thing I always tell new puppy owners: don’t schedule shots on a day when you have a big puppy playdate or training class planned. Give them the rest of the day to just be lazy.
Small Lump at the Injection Site
Finding a puppy lump after vaccine is the second thing that sends people into Google spirals. I totally understand — you’re petting your puppy and suddenly there’s this marble-sized bump that wasn’t there yesterday.
These lumps are called injection site granulomas, and they’re your puppy’s immune system doing exactly what it should. The body creates a localized inflammatory response right where the vaccine was administered.
What’s normal:
| Feature | Normal Range |
|---|---|
| Size | Pea to marble sized (roughly 0.5–2 cm) |
| Texture | Firm but not rock-hard |
| Pain level | Mildly tender when touched |
| Duration | Usually gone within 1–3 weeks |
| Skin appearance | No redness, no discharge |
Don’t massage it, apply heat, or try to squeeze it. Just leave it alone. I made the mistake of constantly checking my first Golden’s injection lump every few hours, which just irritated the area more. Let it be.
If the lump grows larger than a golf ball, becomes hot to the touch, starts oozing, or hasn’t resolved after three weeks — call your vet. But the vast majority disappear on their own without any drama.
Low-Grade Fever
Puppies can run a mild fever after vaccinations. Their normal temperature sits between 101°F and 102.5°F (38.3°C–39.2°C). A post-vaccine temp of up to 103°F isn’t unusual.
Honestly? Most people never notice this one. You might observe your puppy feeling warm to the touch, especially around their ears, or they might be slightly panting more than normal. It usually accompanies the lethargy and resolves on the same timeline — within 24 hours.
Unless you’re already comfortable taking your puppy’s rectal temperature (and I’ll admit it’s not my favorite activity either), the fever itself isn’t something you need to actively monitor. The behavioral signs — sleepiness, reduced appetite — tell you the same story.
If you suspect a fever lasting beyond 24 hours or your puppy seems genuinely distressed, that’s a different conversation.
Side Effects That Need a Vet Call Within 24 Hours
Here’s where we shift gears. The reactions above? Normal. Expected. Not a big deal. But there’s a small percentage of puppies — and I mean small — who have reactions that require veterinary attention. According to AVMA data, true anaphylactic reactions occur in roughly 1 in 10,000 vaccine doses. Rare. But you need to know what to watch for.
Facial Swelling or Hives
This is the one that scared me most when my friend’s Dachshund puffed up like a little sausage balloon about 30 minutes after her shots. Her muzzle swelled, her eyes got puffy, and raised welts appeared across her belly.
Facial swelling, swollen eyes, or hives (red, raised bumps across the body) indicate an allergic reaction. This isn’t wait-and-see territory.
What to do:
1. Call your vet immediately — or head to an emergency clinic if it’s after hours
2. Take a photo of the swelling so the vet can see the progression
3. Don’t give any medication (Benadryl, antihistamines) unless your vet specifically instructs you to
4. Keep your puppy calm and quiet during transport
Most allergic reactions respond quickly to an injection of antihistamines or a short course of steroids. My friend’s Dachshund was back to normal within a couple of hours after treatment. But untreated, these reactions can escalate.
Persistent Vomiting or Diarrhea
A single episode of vomiting within a few hours of vaccination? Not ideal, but not an emergency. Some puppies have sensitive stomachs and the stress of a vet visit alone can trigger it.
But if your puppy is vomiting repeatedly — three or more times — or has bloody or watery diarrhea that won’t stop, that’s a problem. Puppies dehydrate fast. A 10-pound puppy can go from “a little off” to dangerously dehydrated in a matter of hours.
Watch for these escalation signs:
– Vomiting more than twice in a 4-hour window
– Diarrhea that’s watery or contains blood
– Lethargy so severe they won’t lift their head
– Gums that look pale or tacky instead of pink and moist
Difficulty Breathing
This is the emergency. Full stop.
If your puppy is wheezing, gasping, breathing rapidly, or their gums are turning blue or grey — get to an emergency vet now. Don’t call ahead. Don’t wait to see if it passes. Go.
Anaphylaxis is rare, but when it happens, it tends to occur within the first 15 to 30 minutes after vaccination. This is actually one reason many vets ask you to wait in the parking lot or lobby for 15–20 minutes after shots. It’s not just a suggestion — it’s a safety window.
Brachycephalic breeds (Bulldogs, Pugs, French Bulldogs, Boston Terriers) already have compromised airways. Any respiratory distress after vaccination in these breeds should be treated with extra urgency.
Side Effects by Vaccine Type
Not all vaccines hit the same. Puppy vaccine side effects can vary depending on which specific shot was given, and knowing this helps you prepare for what to expect.
DHPP (Distemper Combo) Reactions
The DHPP vaccine — also called the “5-in-1” — protects against distemper, hepatitis, parainfluenza, and parvovirus. It’s the cornerstone vaccine and puppies get multiple doses between 6 and 16 weeks.
This one tends to cause the most noticeable lethargy and appetite loss, probably because it’s stimulating immune responses to multiple diseases at once. The second and third doses often produce milder reactions than the first, since the immune system has already been primed.
Some puppies, particularly toy breeds and puppies under 5 pounds, can have stronger reactions to DHPP. If your Yorkie or Chihuahua puppy is especially wiped out after this one, it’s more common than you’d think.
Rabies Vaccine Reactions
Rabies shots are given as a single dose, typically around 12–16 weeks. In my experience, this vaccine causes more injection site lumps than the others. The rabies vaccine uses an adjuvant (a substance that boosts the immune response), which can create more local inflammation.
Some owners report behavioral changes lasting 1–2 days — their puppy seems more anxious or clingy than usual. My Golden was genuinely spooked by loud noises for about 48 hours after her rabies shot. Not something the textbooks really cover, but I’ve heard it from enough other owners to think there’s something to it.
Rabies reactions tend to show up a bit later — sometimes 24 to 48 hours after vaccination versus the quicker onset with DHPP.
Bordetella (Kennel Cough) Reactions
Bordetella is interesting because it’s often given intranasally (squirted up the nose) rather than injected. And the side effects reflect that delivery method.
Common reactions to intranasal Bordetella:
- Sneezing for 1–3 days (sometimes a lot of sneezing)
- Mild nasal discharge — clear, not thick or colored
- Occasional reverse sneezing episodes
- Very rarely, a mild cough
Don’t panic if your puppy starts sneezing after a Bordetella vaccine. It doesn’t mean they caught kennel cough. The intranasal vaccine contains a modified live organism that causes a local response in the nasal passages. It’s doing its job.
The injectable version of Bordetella tends to produce reactions more similar to other injected vaccines — some lethargy and possible injection site tenderness.
How to Comfort Your Puppy After Vaccinations
You can’t prevent side effects entirely, but you can make the recovery window more comfortable. Here’s what works — and what doesn’t.
Do this:
– Let them sleep. Seriously. As much as they want.
– Offer their regular food but don’t stress if they refuse a meal
– Make sure fresh water is always available
– Provide a quiet, comfortable resting spot away from household chaos
– Avoid touching or pressing on the injection area
– Skip the dog park, training class, and vigorous play for 24 hours
Skip this:
– Don’t give human medications (no Tylenol, no aspirin, no ibuprofen — these are toxic to dogs)
– Don’t ice the injection site unless your vet specifically tells you to
– Don’t restrict water thinking it’ll prevent vomiting
– Don’t schedule baths or grooming on vaccination day
I always plan my puppies’ vaccination appointments for late morning. That way they have the whole afternoon and evening to sleep it off, and by the next morning they’re usually back to their ridiculous selves. It’s a small scheduling trick that saves a lot of worry.
And here’s something nobody tells you — your anxiety transfers to your puppy. If you’re hovering over them every five minutes checking for symptoms, they pick up on that stress. Check on them, yes. But then go about your day.
Should You Separate Multi-Pet Households After Shots?
This comes up a lot in homes with multiple dogs. Short answer: you probably don’t need to, but there are a couple of situations where a little separation makes sense.
Vaccinated puppies aren’t contagious to your other pets. The injectable vaccines use killed or modified organisms that can’t spread. Your older dog isn’t going to “catch” anything from your recently vaccinated puppy.
The one exception: intranasal Bordetella. Since it uses a live (modified) organism delivered to the nasal passages, there’s a theoretical — emphasis on theoretical — risk of shedding. In practice, this almost never causes issues in healthy adult dogs. But if you have a very old dog, an immunocompromised pet, or a dog currently on chemotherapy, keeping them separated for 48–72 hours after an intranasal vaccine is reasonable.
The more practical reason to separate? A cranky, sore puppy doesn’t want to be bothered by a rambunctious housemate. If your older dog likes to play rough or won’t leave the puppy alone, give the vaccinated pup a quiet space for the rest of the day. It’s less about disease risk and more about letting them rest in peace.
Frequently Asked Questions
How long do puppy vaccine side effects last?
Most side effects resolve within 12 to 24 hours. Injection site lumps can persist for 1 to 3 weeks, which is still normal. If any symptom — lethargy, appetite loss, fever — lasts beyond 48 hours, contact your vet.
Can I give my puppy Benadryl after vaccinations?
Only if your vet specifically instructs you to and provides a dosage. Never give any medication without veterinary guidance. The correct Benadryl dose for dogs is 1 mg per pound of body weight, but this isn’t something to DIY — especially with a small puppy where dosing precision matters.
Are certain breeds more likely to have vaccine reactions?
Yes. Toy breeds and brachycephalic breeds (Pugs, Bulldogs, French Bulldogs) have slightly higher reaction rates. Dachshunds also show up frequently in adverse reaction data. Larger breeds tend to handle vaccines with fewer visible side effects — though that doesn’t mean they don’t experience them.
Should I avoid exercising my puppy after shots?
Keep things low-key for 24 hours. Short potty walks are fine, but skip the dog park, puppy class, and any vigorous play. Your puppy’s immune system is busy — let it work without the added physical stress.
Is it normal for my puppy to cry or whimper after vaccines?
Some puppies are more dramatic about it than others. Mild discomfort at the injection site is normal, and some puppies will whimper if you accidentally press on it. Constant crying, yelping when touched anywhere, or signs of severe pain should be reported to your vet.
Can puppies have delayed reactions to vaccines?
Reactions typically appear within the first 24 to 48 hours. However, injection site lumps can develop over 2 to 5 days as the local immune response builds. True delayed allergic reactions beyond 48 hours are extremely rare. If your puppy develops new symptoms a week after vaccination, it’s likely unrelated — but mention it to your vet anyway.
Watching your puppy feel crummy after vaccinations is never fun. But these shots protect against diseases — parvo, distemper, rabies — that are genuinely life-threatening. A day of sleepiness and a skipped meal is a very small price for that protection.
Trust your gut. If something feels wrong beyond the normal tiredness and mild soreness, call your vet. They’d rather hear from a worried owner over nothing than miss a real reaction. And remember — by tomorrow, your puppy will almost certainly be back to chewing things they shouldn’t and zooming around the house like nothing happened.
Featured Image Source: Pexels
