There are a number of conditions that bar you from donating blood. He traveled the world in his youth and contracted malaria. That permanently bars you from donating because the parasite that causes malaria can't be gotten rid of, at least with our current knowledge. Or he takes blood pressure medication. Some young people have a genetically based blood pressure problem, and you can't donate if you take blood pressure drugs. Or he recently had a tattoo. I know that for some period of time after a tattoo is done, they won't allow you to donate (I think it's about a year.)
Nan
