Said It Here

Lump on cat after vaccine

Finding a lump at a cat's vaccination site causes immediate panic, driving owners down anxious internet rabbit holes while they wait to see if it will go away. Some experience deep distress and regret over getting the shots if complications arise.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    Monitoring the lump closely for changes over a week or two
  2. 2
    Calling the vet for guidance and waiting to see if it disappears on its own
  3. 3
    Sending pictures to the vet or bringing the pet back for an in-person examination if it persists
  4. 4
    seeking reimbursement from pharmaceutical manufacturers
  5. 5
    managing symptoms with medications like MiraLAX and cisapride
  6. 6
    increasing moisture in food to help with constipation
  7. 7
    using gentle saline wound care for open tumors

In their words

Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.

r/cats4 people · September 2026 – October 2026

“I WISH I HAD A TIME MACHINE AND GO BACK TO DECEMBER :( I KNOW ITS NO ONES FAULT CANCER KILLED YOU AND NOW CANCER DIED TOO IN ORDER FOR IT TO BE COMPLETELY GONE IT HAD TO TAKE YOU.. IM SO SORRYYYYYYYYYY.. PLEASE EDUCATE YOURSELVES PLEASE!!!!!!!! THIS IS FOR YOU ISABEL!!!!!!!!”source ↗

crazygirlcindy · r/cats · 91 upvotes

“and yes BABY GIRL IF I CAN GO BACK TO DECEMBER I WOULD’VE SAID NO TO THE SHOTS!!!!!!!!!”source ↗

crazygirlcindy · r/cats · 9 upvotes

“Yesterday I noticed she has a lump on the area (behind her arm) which hasn’t happened before. Called my vet who said to monitor it, but of course I googled it and spiraled down some concerning rabbit holes.”source ↗

Chemical-Post-6640 · r/cats · 8 upvotes

“When my cat got his vaccine he had a lump above his back leg at the injection site for a couple of weeks. It made me very anxious so the vet was going to examine it during his booster.”source ↗

AeroMech11 · r/cats · 2 upvotes

“my kitten had to have a bunch of vaccines before we could adopt her, and developed a superficial clot in the area. It scared me but vet also said to monitor, and it slowly went away in its own.”source ↗

little_axolotl14 · r/cats · 1 upvotes

Where this came up

People with this problem also raised