Chagas Disease
You cannot give blood if you ever had Chagas disease even if you are fully recovered.
You cannot give blood if you stayed or worked in a rural subsistence farming community in South America, Central America or Southern Mexico for a continuous period of 4 weeks or more. (NB: rainforests are not considered to be rural subsistence farming communities)
You cannot give blood if you or your mother was born in a Chagas risk area; this includes South America, Central America and Southern Mexico.
See list of countries for Chagas risk areas.