Hives (again) and swollen sheath (again)

Joy V

I've posted 3 posts about this issue to-date; for far had one response.  I deleted the other two because ... crickets.  Things are looking much worse now, and I could use some help/direction please.

Tuesday (05/26) my horse broke out in hives on his neck, chest & shoulders.  This is everywhere a lining was in his (new never washed) fly sheet.  Normally I cut the lining out, but didn't on Tues.  I assumed the heat and the lining caused the hives.  I cold rinsed him & sponged with 50/50 vinegar/water.  Next day (Wed) hives looked better in the am, but not gone.  Cold rinsed/sponged him again (AM & PM).  I also ordered large bottle of generic Benedryl because our store was out of it (and zyrtec). 

Cold rinsed/sponged on Thurs.  Hives looked worse in the am, better in the PM - Benedryl arrived Thurs PM.  Dosed him with 20 25mg caplets (at the direction of our vet) melted and poured over his bucket of supplements.  Friday AM hives looked worse again, dosed him AM w/ generic Benedryl, cold rinse/sponge.  Hives looked better Friday eve - noticed new, localized swelling on his abdomen - looked like an insect bite, so dosed again w/ Benedryl, cold rinsed/sponged.

This morning his hives were worse again, but also, his sheath was extremely swollen.  Dosed w/ Benedryl.  Cold rinsed/sponged, also cold rinsed sheath for about 15 minutes, hand walked for about 20 - 30 minutes, and dosed with 1/2 dose of banimine that I have from the vet, and I did text the vet right away.  Just went back to the barn and his sheath is more swollen, so cold rinsed again, hand walked, and because I haven't heard back from the vet, called Loomis.  Vet is off today per Loomis and their on call vets are covering.  They said they will have a vet call me.

Have not heard back from Loomis vet yet.  What is the protocol at this point?  Pentosan?  I'm just really worried that he might not be able to urinate, the sheath is that swollen.  This afternoon, he also has swelling on his chest, right at the corner of his legs, where he's normally smooth.  He's eating normally, pooping normally, and moving well.  He is definitely a bit itchy, but not horribly so.  I did put a mix of zinc oxide & swat on his sheath because flies were landing and I wanted to protect it.  

I added photos to my album.  The back leg looks like it has hives in the pic of his sheath, but it doesn't, it's his hair.

I am just pretty worried about him.  He's always had terrible seasonal allergies.  I assumed it was because of the uncontrolled IR.  But he has been on tested hay now for over 2 weeks, he has been so doing well, but this is just such an out of control-seeming reaction allergy-wise.

Thanks for any input.  Sorry I have not updated my case file to add this event yet.

Joy and Willie  
(aka FLS Boxcar Willie)

Nevada County, CA - 2019

Case history:
Willie's photo album:

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