I can't help but think of my little old Aunt, that died with "being allergic to the sun", from Lupus, and she also had Bell's Palsy (which I now know can be a Lyme symptom).
When I had the high D on the EPFX, with the RMSF, I was trying to keep covered from the sun when I did yard work/gardening, but that must be one of the reasons people with MS and Lyme have a hard time with the sun and heat?
My aunt always wore long sleeves, gloves, pants, and a big floppy hat if she was outside for even a few minutes.