1. If you're up for spending the money, I would call Don at Herbs4Horses and ask him for a two pound bag of the "Allergy Herbal Blend" but, you'd have to take your horse off the Anti-Hist and the Dex.
If you're going to see any improvement, you should see something degree within 48 hours. A two pound bag would give you plenty of time for improvement without spending a lot of money.
2. Believe me, I am ON the Omega-3 Horseshine side of the fence - I can't say enough good about it. I'm sure it helps with minor allergy issues but, anyone in my barn with allergies --- it isn't minor - lollol I live in the Tennessee Valley, a/k/a The Basin, or as one vet puts it "Allergy Purgatory".
My allergy-laden horse didn't have these problems until we moved here and the born/raised-in-this-county Vet once told me I am lucky enough to live on the worst end of the county
3. Maxi-Glo is what I use - it comes in meal and pellet forms. I buy the pellets. My horses like the taste - lol lol lol
Your horse still needs a good quality ration balancer to get all his vitamins/minerals in him. The rice bran doesn't offer anything in that regard.
Two of my horses are finishing up EquiPride (I can't make that 92 mile one-way drive anymore) and the other two are on Triple Crown (that's "only" 41 miles away:(
Triple Crown's ration balancer (RB) is called "30%". My 26 yr old Arab is on that and doing wonderfully.
My 25 yr old TWH is on TC Senior as he doesn't seem to get as "off" on the Senior as he did on the 30%. He's my heart horse (the guy in my avatar) of 22 years and now has EQuine Metabolic Syndrome, hind gut ulcers and the vet is sure he also has lipomas in the digestive tract. His health issues have made it tough to keep food in him without him colicking, which that's it's own story.
Anyway, when the barometric pressure makes a big change (like when the outer edge of Isaac first started rolling in), I take him off his TC Senior at night and just feed him rice bran, Omega-3 Horseshine, crushed apples & carrots. It's gotten to where I breath a HUGE sigh of relief when he goes straight to is hay after eating his supplements at night.
I said that to sort of say, yes, both the environmental and weather changes can make a difference to many horses (regarding your conversation with the Gent in TSC
I don't know how long you've owned horses but if it's been a fairly short time, believe me things didn't used to be this way.
My first set of Keeper Horses lived 85% of their lives "Before Coggins" and shots were unheard of, unless you showed heavily on the circuit.
I never had problems. I sent those two Fellas on to their ancestors at ages 27 & 29 with nothing more than the Arab/Saddlebred needing stitched up when he was a two year old. He went on his last hard, all day trail ride, when he was 27. He finished that ride ahead of at least 50% of 175 horses; that was his idea, not mine, I let him set his own pace
All these health issues, allergy problems, founder, etc is a whole new thing for me. It is no exaggeration that I have spent more in equine vet bills these past five years than I have spent since I bought my first Keeper Horse 53 years ago