Vaccinations save millions of pets, so it’s a small price to pay if our furry friends have some mild side effects. But an allergic reaction is something different entirely.

Minor side effects occur within hours of vaccination and are pretty common. They might include soreness or swelling at the injection site, a slight fever or mild lethargy. Nasal vaccinations can cause some coughing, sneezing or congestion for a few days. Just watch your pet until signs diminish — but see a veterinarian if they linger.

Allergic reactions generally occur within minutes of vaccination but may develop hours later. No matter the timing, they’re always emergencies. Signs can include vomiting or diarrhea, hives or facial swelling, trouble breathing or collapse.

Because nothing’s perfect, take the time to monitor your pet after vaccination.