Crisis Time: Equine Pemphigus Dermatitis

Welts/bumps covering her neck, under belly and some on the legs. 
Oh my. Yes, it's been a bit of crisis time around the farm. In addition to everything else we have going on, our newest mare was recently diagnosed with Pemphigus Dermatitus. It is an auto-immune disease that seems to come out of nowhere. Within 1-2 weeks of bringing Krystall to the farm, she started getting what seemed to be a rash or hives. After another week with the condition getting worse, it was time to call out the vet.

Another week later with no results from the first vet's diagnosis, we went to the Idaho Equine Hospital for further evaluations. Further evaluation$...blood work, skin biopsies, hair folical exams and a team of specialists working on her ca$e. Can you $ee what's frustrating me? ;) In addition to this, she was also diagnosed with 3 bacterial infections. Yes, THREE.
This was where it started, with hair coming off by the handful on her back leg

I'm not at all convinced that this is a correct diagnosis, so I'm asking for help. 

The only things that have changed for her since coming to our farm, is new hay, which she wasn't thrilled with, new grass pastures (to her), she was also de-wormed. Her prior owner said she's never even had a runny nose in her 11 years (she has owned her since a weanling), so this is as much a mystery to her as well.

All those black spots are the hair folicals waiting to come off with hair attached
We've had the county extension agent over and walked the pastures to see if there was something she got into, but she said, no there wasn't anything poisonous for horses. Not sure though if that would mean she couldn't be allergic to a specific grass or weed ...Or in the new hay? Mind you, we also have Elsie Rose, who just came in as well, with none of these issues and was in the paddock next to her, sharing a water trough, until we quarantined Krystall.

Those aren't shadows, they are the lumps/welts/ whatever you want to call them, all over her neck, shoulder and chest
She has been in quarantine for 5 days now and we've changed her hay over to a simple grass hay with 3 cups of LMF Super Supplement.

She is now getting 250 mg of Prenisolone once a day (noonish) for the dermatisis, and 8,000 mg of Sulfamethoprim twice a day (morning and evening, 16,000 mg total) for the bacterial infections.

She started here about 250-300 pounds overweight. Her weight now looks normal at around 900/925 lbs, but she was about 950, 10 days ago when we went to the vet, so she has been losing weight. We have upped her hay so she always has it in front of her now to keep her from loosing too much weight as can happen with the meds.

Anyone have any thoughts?


  1. Anonymous4/21/2012

    Hi Corinne, It is Carla(Krystal's neighbor). Oh my gosh. She looks awful. The years I've known her, she has never had a lump, bump or anything wrong with her. She obviously has had an allergic reaction. Am thinking weeds, especially if she were on a diet. She would devour anything in reach. There are so many reactive weeds in this part of the country(hoary alyssum, buttercups, wild parsnip, leafy spurge, lupine, larkspur and so on) A lot of them cause swelling and dermatitis. I would seriously consider getting her on an antihistamine. Maybe there's a topical rinse that would also give temporary relief. Dr. Alan Clark in Albion (208-673-6632) is the best. You can email him photos and all info. There is a good horse vet in Baker that I'm trying to get a number to. Would seriously look at the hay. Maybe any sprays that have been used. Back to the weeds...maybe in the baled hay. Hoary Alyssum likes to grow in hay fields. What wormer did you use. Would compare it with what Carol had been giving. Am just rambling with thoughts. There has to be something she has had at least contact with physically if not digesting it. I'd look at the soil and any sprays/chemicals that might have been used. Insects. Possibly no-see-ums or wasps somewhere that she has gotten into. Maybe drop any supplements that are new to her. Fly sprays or anything topical that could be reacting. Would definitely dry lot her away from anything growing. Has water been checked. I think Dr. Clark is the best bet. I hope she finds relief soon. Breaks my heart...carla

    1. Anonymous4/22/2012

      Try her on the Bach Flower remedy Crab apple put it in her water. Approx 10 to 20 drops depending on the size of her trough.It will help detox from the inside out. I hope this helps, good luck!

    2. Thanks for the info! Yes, we're thinking hay too. I am in search of better hay. Actually thinking we'll be buying our hay from either N. Idaho or E. Oregon. WAY too many weeds here in the "grass" hays.

  2. Anonymous2/12/2018

    Was the new hay she was introduced to heavy with ryegrass/clover/alfalfa?
    Are the hives weeping, becoming crusty and patches of hair falling out?
    it could be photosensitivity caused by sun sensitive pigments in these grasses - which the horse ingests and these plant pigments make their way to the unpigmented skin of a horse for the UV rays to oxidise the skin, cause hives, weeping, hair falling out.
    (avoiding UV rays is impossible, they pass through cloud on a cloudy day - its not the sun causing skin to burn but the UV rays of the sun which are about from sunrise to sunset if you walk outside - unless you keep the horse locked up 24/7 which is pure abuse we know!)
    So i suspect the new hay contains the known grasses or weeds which cause the pigment to build up on the INSIDE of the horse.
    You don't necessarily have a horse that's sensitive to the sun, when these pigment heavy plants are eliminated from their diet.
    I suspect i am having this problem with my horse this winter - haylage is heavy with ryegrass species...the black mare unaffected - him grey/roan - covered in lumps, weeping, hair falling out. Ireland is crap for hay - its all mouldy so im using haylage but its all made out of ryegrass! I'm seriously running out of options for forage ...good luck with your bumpy babe :-)