A sty is an infection of the secretory glands, related to the eyelash follicles. Generally speaking, styes occur when the secretory gland’s exit to the edge of the eyelid is blocked encouraging the growth of bacteria and formation of painful infectious lumps and purulent discharge. They most commonly occur among patients with predisposed conditions such as blepharitis. As a sty is an infection, it appears after you rub your eyes with dirty hands, use out-of-date make-up or are around contaminated substances and—above all—in contact with infected individuals. The most frequently associated agent is Staphylococcus aureus, which is found on the skin and in the nasal cavity. It usually does not present with complications, but it may occasionally cause styes. Since it is related to an infectious process, a sty is highly contagious, so you should not share towels, tissues or other personal belongings with members of your family or household.