In Seattle I've tried to donate blood multiple times over the last decade.
Every time, "because I've been to India in the last 5 years" they are unable to take my blood. Something about the risk of malaria. At worst, given a shortage, why not take my blood and analyze it? maybe even clean it (like with a dialysis machine)?
Talk about a dumb rule. Anyways... is there some other way to get this advantage? Are there blood letting doctors?