You cannot give blood if you are a man that has had sex with another man. Even if it was only once and you used a condom. That to me smacks of homophobia and takes fears/precautions too far.
I have been refused giving blood, some rubbish about a type of head opperation done on me back in 1984, I think it is rubbish and if they used the wrong chemicals on me then I should be able to sue them for it now.