Nettles is not really very effective for this, it is nice the person wants to use local plants, but that is very limiting, use what works. I would use immune amphoterics.
For dry, itchy red skin issues I would add Sarsaparilla, Turmeric and Yellow Dock to the Milk Thistle, Burdock seed and Gotu Kola, these 6 herbs would be a very good starting formula.
I would start 6-8 weeks before it gets hot and humid, which may be the triggers for the flare.
I cannot speak to Canada but H & A makes Burdock seed tincture and some of our products are sold in Canada under the Tall Grass label.
Burdock root does nots do what Burdock seed does, and Marshmallow will not help.
Fish oils and 5 Defenders - good...Astragalus and Dang Gui could help.