Just looking for some arm chair vet opinions while waiting for the vet to come out tomorrow - 19 year old OTTB with ventral edema on his belly and between his forelegs. He looked slightly distended last night and this morning he had clear ventral edema (though not in his sheath and none in his legs). However, he has lost a lot of hair along his belly and side and the area of hair loss all seem to have a lot of small scabs or blood blisters. If my thermometer is accurate, his temp was below average but he isn’t acting cold. No loss of appetite, and stool is normal. We put him in a blanket due to the bald spots and the cold temperatures, but normally this guy is a super easy keeper and has the coat of a woolly mammoth. There has been a history of Lyme disease that resolved with treatment a few years ago. He had a recent fecal test and came back with a 0 for an egg count. He is turned out daily so has not been stuck standing in a stall. Dr. Google and books have not yielded a lot of information. He is a retired saint of a horse, so it is just a matter of quality of life at this point. Soundness issues ended even his being a trail horse, so we just want him fat and happy in the pasture. The posts that I found on COTH are a few years old and don’t quite match up.
Could the hair loss be from serum leaking? We had one that had a tumor that caused fluid build up - they drained liters out and it returned. Vet originally thought tick bite, but ultrasound proved more serious.
Could it be a kick? We had a mare that took a chest kick and developed a pendulous swelling between her front legs.
Anyway, could be nothing, could be something. As always with horses. Hope it is nothing!
Wild guess but maybe he rolled in ants then was allergic to their bites?
Was he recently vaccinated or otherwise stressed?
Consider Pemphigus. Rare in horses, but I have a Paint here who was given to me to try to keep alive after he developed Pemphigus after vaccinations last spring. The spots eventually swelled up and became pus filled, Mostly on his face, neck, chest and between the hind legs…basically where he sweat.
What area of the country are you in?
I’m in the Southeast and the temperatures have been way above normal.
Which means ticks and other parasites may be becoming more active, or weeds and grasses that can cause an allergic reaction may be coming up.
What is your deworming protocol?
No experience to add. Just wanted to send jingles for your boy, and you. Please let us know how the vet appointment goes. 
{{{Hugs}}}
Thanks all. We are in the northeast with a mild and muddy winter. We did have a mare once that developed ventral edema but it was probably from a kick. There was not a single other symptom with her other than the edema which was impressive and years later now, she is right as rain. This gelding has all of the hair loss along one side and under his belly over a pretty large area. He was dewormed with Quest Plus in November and just had a fecal count with an egg count of zero. Hopefully the vet finds something that can be addressed and is fixable.
This happened to my COPD/Heaves mare during a bad attack. It was scarier because it looked so wierd to see all that fluid filled tissue hanging. Has never happened again and we used Dex and Ventipulmin like we always do. Just one 5 days treatment taper down and all of it all went away.
For what that’s worth.
Hope you get your boy well soon!
The vet came and says that his heart and gut sounds are all good. Bloodwork and hair samples are being sent out. For the most part, all of his hair on his belly has fallen out and he has massive bald spots. He started shedding this week and has a had a few thorough groomings so we know the hair didn’t start falling out before the last few days. Edema has not gotten worse. Hopefully, the blood work or hair samples provide some information.
Has he had any past allergic reactions to anything? Did your vet and your other research all point to a systemic reaction?
With my heaves girl, Ohio State did a skin test and wow was she highly allergic to a lot of things. And I should add that skin test was a few years before the ventral edema.
PaddockWood - he is an older OTTB that has had Lyme disease and has been tested/treated in the past. Once we get back blood work/skin scrapings/fecal counts to rule out some issues, I think we will need to look into some sort of allergy issues. We have had such horrible mud the last few years (no longer get a winter with snow, we alternate between warm mud/cold mud/frozen mud with a month or two of drought during hay season), and this horse has struggled with rain rot despite all attempts to mitigate it (that work for the other horses). I would not be shocked if there is an allergy issue. At this point, I am just so relieved that it isn’t congestive heart failure - but also want to get it sorted out and keep this guy comfortable and not half bald on his barrel. Thanks for the insight and well wishes.
