My gelding 11 yrs took a reaction only once to a flu jab and after phoning the vet he said it was normal and something to do with the rea where they injected (it was on his neck) his took about 2/3 days to go away.
As long as horse seems fine in itself should disappear in a few days. We had a horse who developed a lump after her flu and tet but se became very stiff and would barely walk. It was just a severe reaction to the injection but put her out of action for weeks so keep an eye on it!
Ok thankyou
Yes vet said to keep eye on it but that's all
She seems well in her self ie eaten and drinking etc but just really unhappy being touched from ears down to withers
On left side with lump
yep on his neck it was the size of a fist and got vey hot he had to have 5 days antibiotics - like you I had never seen this I was really worried about him and I have not updated his flu because of it
Benson always got a lump and a very stiff neck after flu jab, so much so we had to put his water and feed up on the frame on the door for a couple of days. In the end the vet dfone his jabs in his chest and not his neck, and no reaction.