I was told with my old horses haeomatomas to cold hose for 10 mins a day and they went in 2 days
They reckon if you drain them you are actually braking the skin so you are introducing a risk of infection....
On the other hand my mare has one which looks like it's caused by work, it keeps going down slightly when I hose but fills right up when I ride so I'm waiting for the vets to call me back..
My mare had one and the vet said to leave well alone. He said it would go on its own and it did. It was huge and took three weeks to dissapear but no sign of it again. I too think you risk infection if you open it up or drain it with a needle.
Leave alone. My horse had one between front legs (been kicked). It was like a water melon. Vet advised to cold hose and not drain.If you drain it it may get infected and fill up again. It took6 weeks to go completely and never came back.
I had one myself after horse bite - went darker after exercise but then reduced again (side of knee) is still there slightly after a year ! I was told just to exercise to get blood moving but they wouldnt do anything else - also told not to massage it or anything as could increase risk of blood clots!
My sisters mare had one in her foot, they removed it and when she broke her in she couldn't move right but we thought it was just her conformation, now she is moving better than ever, they think it formed from an abcess when she was a foal. Good luck xx