I first noticed these come up about a month ago. Honey, being on a rather simple diet of hardly any grass, good quality meadow hay and fresh water (due to the simple fact that she was like a balloon and still is a smaller version of said balloon) naturally tries to grab at any grass she can outside of her paddock in her tie up area and had gotten desperate in grabbing the strands in between a weed that I had yet to remove and in the end ate a chunk of it. Not knowing if it was poisonous or not, when I noticed the "welts" I guess would be the best description, I put it down as a reaction and thought they would go away. (Weed was instantly removed)
However they haven't. It's been a pretty darn hot summer here in New Zealand, and I'm wondering if they have something to do with the heat. She seems completely unphased by them, still eating and drinking and therefore excreting very healthily and is in work and not showing any signs of being under stress.
Her diet hasn't changed - she's been on said diet just before spring hit and much to her disapproval, has barely been allowed any spring grass and is slowly strip grazing her current paddock down.
I'm not too bothered by them, but since they've stuck around a bit, I just thought I'd find out if anyone else has dealt with something similar before? I haven't monitored if they get smaller on days that are cooler as we've had unnaturally cold snaps a couple of times in the past week, but apart from that its been one hot summer and do vaguely remember something to do with sweating and glands... but this is me sounding very uneducated and I don't want to assume anything without a basis of factual knowledge!
The weirdest thing is that its only on that side of her body - NOT on her right neck/shoulder. The other thing I have to mention is that her paddock we ride in is currently higher than I'd prefer (went from two horses to one, and with her basically on a hay diet and me yet to get a topper in, I have a fair amount of grass about!) and there are grass seeds. But if there was any affect from this, surely it would appear on both sides, rather than just her left side.
If there was any change in behaviour/basic vitals I would have contacted a vet by now but since there hasn't been, I just thought I'd throw it up here.