As such, quarians are given various vaccinations and immunizations to help ward off disease. After living aboard the Migrant Fleet for generations, the quarians' immune systems have atrophied further still due to the years in the sterile environment of the Migrant Fleet. Furthermore, what few viruses and other microbes were native to their homeworld were often at least partly beneficial to them, giving them a symbiotic relationship with their environment. Quarian immune systems have always been relatively weak, as pathogenic microbes were comparatively rare in their homeworld's biosphere.

A quarian's lifespan is roughly equal to a human's, but is prone to be less if infection breaks into the suit. Along with their suits, quarians also have extensive cybernetic augmentations integrated into their bodies. Their suits can be compartmentalized in the event of a tear or similar breach to prevent the spread of contaminants (similar to a ship sealing off bulkheads in the event of a hull breach). As a result, all quarians by necessity dress in highly sophisticated enviro-suits, to protect them from disease or infection if they are injured. The most distinguishing feature of quarian biology is their weak immune system, compounded by centuries of living in sterile environments. Male quarians, however, appear to lack a third toe. Aside from hands and legs, their general body shape and sexual dimorphism is similar to humans. Their lower legs are bowed backwards significantly, compared to asari or humans. They also have three thick fingers on both hands which include a thumb, an index finger, and a long finger, similar to the middle fingers for humans, as well as three toes on each foot. Quarian facial structure and hair actually makes them the most similar to humans in physical appearance. Their eyes can see into the ultraviolet end of the spectrum their suit HUDs can show information in those wavelengths. Their ears or ear analogues differ in a noticeable fashion from those of humans, with references made to 'what for the quarian version of an ear'. Quarians have an endoskeleton, lips, teeth, and two eyes with eyelids and tear ducts. Quarians are generally shorter and of slighter build than humans.

Mass effect 3 quarian face revealed