Few have ever seen the ugliness that lies beneath a Jawa mask. Jawa faces are obscured by a cloud of insects that gather in the recesses of their hoods, attracted by their foul odors. Their particular stench is a combination of poor hygiene and a mysterious solution into which Jawas dip their clothes to retain moisture. To Jawas, the odor is packed with information about each other, such as clan lineage, health, emotional state, even the last meal eaten.
Jawas have evolved several important survival traits, such as exceptional night vision, a strong immune system, and an efficient digestive system that draws all the needed nutrients from the Jawa staple diet of hubba gourd.
(JUST GO WATCH FRIDAY THE 13th PART 7 AND YOU'LL SEE A JAWAS FACE)
http://www.starwars.com/databank/species/jawa/?id=eu
GO and readm you'll learn sumthin.