My arab gets the same, his is an allergy to fly bites. Usually we can feel them and apply antihistermine to area. In a few days swellen goes down and back to normal
What did they say at the equine hospital? One of my horses had a swollensheath this past month and we gave him Azium (Dexamethasone) and did a thorough cleaning. That seemed to take care of it, but I can say that the heat had a lot to do with how swollen it was. It has been so hot this summer that many horses' sheaths, legs, etc are swelling up.
Our welsh x had a big lump on his belly and a swollen sheath this month. My vet declined to give him dex due to the laminitis risk and just had me cold hose it. It went down slowly over about 2-3 weeks. It appeared to be a reaction to a spider bite or some other nasty bug.
Read Dr. Epsy, AAEP(equine reproductive specialist) Comments of
Myth to regular sheath cleaning.
http://www.aaep.org/info/horse-health?publication=819
Summary:
What looks like dirt is natural accumulation. Horses in wild never have sheaths cleaned.
We've never had a problem with swollen sheath in any gelding until I read an old book that states to regularly clean it. So, I cleaned it out of guilt and Now my horse has a swollen sheath!
I agree with above vets that swollen sheath can arise from a number of factors. One seems to be from cleaning/disturbing via cleaning when not warranted. So check concerns with a vet first and remember: interior genitals maintain own natural environment that shouldn't be disturbed unless something goes amiss first. What looks like dirt-simply isn't. Instead its the very natural accumulation of oil and lubricant. Read the reproductive specialists comments and Disregard old books: Don't disturb to clean a penis/sheath that's functioning well. and never with a garden hose that may cause internal water damage.