Have his selenium level checked, it may be high. Many people are finding high levels even though they don't take supplements.
We need to be careful with grains because the whole state of South Dakota is putting out so much high selenium wheat and other grains that they supply much of the country now. There is no regulation on the growing of grains in high selenium soil and no regulation about selling it. No matter how dangerous the level. When you make gluten, you concentrate the levels of everything that is in the grain.
Nails and hair are usually the first indicators of Chronic selenium toxicity. A person would have to not eat to have a deficiency. It's in the meat because the animals are eating high selenium diets. So virtually everything has selenium in it and it accumulates in the body. The body just can't get rid of the excess fast enough.
Please let me know if you get a test. I am keeping track of how many people I can find with high levels. I have a theory that many people are toxic. I have already found many toxic livestock in several different states.