Diplosian

The Diplosians are a race of humanoids native to Diplos. They look similiar to silvery-skinned humans, though they have unusual biochemistry and an allergy to citric acid. Cessair of Diplos lived for over four millennia, though this may be a result of her access to the Third Segment of the Key to Time, rather than a racial characeristic. (DW: The Stones of Blood)