Lots of people here take selenium. Whilst this is a valuable supplement if you are lacking, there are limits and unpleasant effects of taking too much. The level of selenium when this happens is quite low so if you have any of these symptoms, cut back.
The Office of Dietary Supplements reports that high levels of selenium in your blood, defined as a concentration of more than 100 micrograms per deciliter, causes selenosis. The symptoms of selenosis include fingernail loss, skin rash, hair loss, weight loss, fatigue and irritability.