A sty is an infection of the eyelid resulting from a blocked oil gland or a Staphylococcus aureus. They can also be brought about during times of stress, poor nutrition or sleep deprivation. They are similar to chalazia, but tend to be of smaller size and less painful, with no long term consequences. They are characterized by an acute onset and usually short in duration compared to chalazia that are chronic and usually do not resolve without intervention.