Hawthorne is great for blood pressure and Red Clover/Stillingia will cleanse out the kidneys. Your friend also needs to drink lots of ACV/Honey water. (1 tablespoon apple cider vinegar and 1 tablespoon of honey in a glass of water)
The first time I put a pound of Epsom Salts in my bath water, my back burned like crazy for a few minutes. I am sure it was pulling some residual toxins out, as I'd had a rash all over my back about a year earlier. Apparently it sucked all the impurities out with the first bath, because it never has burned me again.
So...perhaps the "allergy" to Epsom Salts is a cleansing and detoxifying effect?
Try pouring a pound of regular Sea Salt in your bath water every other night. Alternate with Epsom Salts , and use less epsom salts. If the ES is burning because it's pulling gunk out of your system, the burning will stop when all the toxins are gone.