Tom, one of the Others, used a fake beard as well as some ragged clothes as a disguise during his encounters with the survivors of Oceanic Flight 815. Along with Tom, all of the Others that encountered the castaways wore ragged clothes in order to create the impression that they were uncivilized and undeveloped and to hide the fact that they lived in houses and were more advanced than they look.

Tom removes his beard at the Pala Ferry dock. ("Live Together, Die Alone, Part 2")  (promotional still)

In one of Claire's flashes from the time she was held captive by the Others, Tom approached Ethan in the Staff, in Claire's field of vision. He was not wearing his ragged clothes or his beard but looked clean and shaved.

About a month after these events, Claire, along with Kate and Danielle Rousseau, discovered the station and found a locker room where the beard, theatrical glue, and some ragged clothes were contained. ("Maternity Leave")

The glue had the same style of label as the Vials. It also had RX-1 GND written on it, suggesting that the disguises were part of the DHARMA Initiative experiments.

During the prisoner's exchange at the Pala Ferry dock, Kate revealed to Tom that they knew his beard was fake. Tom then removed his fake beard, commenting that it itched. When Ben arrived at the dock with the Others' boat, he asked Tom where his beard was. Tom said that the survivors knew it was fake.

Tom with and without the beard.

See also