I've had a persistent problem with Toenail Fungus that made my nails get thick and turn inward like claws. I had read an article in Dr. Mercola's website that had a paragraph in it saying to expose feet to sunlight. I was living in the SF Bay Area (cool and foggy) so it wasn't practical but now I've moved to a climate that is more sunny (Albuquerque) and I started wearing sandals in April. My toenails aren't so curved in any more and they don't hurt so much when I trim them.
This is the link to his article. Scroll down to the paragraph titled "Using Sunlight to Treat Chronic Toenail Fungus Infections"
EC: Interestingly, the Mercola article also references Blue Light and Sunlight for antibiotic-resistant infections. Earth Clinic happens to have a Remedies page on this, created years ago! Click the link above to check it out!