Is a Sty Contagious?

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Sty Risk Factors

Foreign substances, such as makeup and dust, can clog the gland's opening if they are not properly washed away. Infections, burns, or trauma resulting in scar tissue can also prevent the glands from properly draining. Sluggish outflow of the sebum (oil) from the meibomian glands is commonly seen in a chronic inflammatory condition called meibomian gland dysfunction (also called meibomitis).

What is a sty?

A sty is a localized infection with inflammation of the eyelid margin, usually involving eyelash hair follicles or eyelid glands (meibomian glands). A sty (also spelled stye and also termed a hordeolum) is usually a painful, reddish, and swollen area on the eyelid margin and is caused most often by the bacterium Staphylococcus aureus (about 90%-95% of cases).

Is a sty contagious?

There is some disagreement among experts about the contagiousness of a sty. In most individuals, a sty develops when some normal occurring and/or transient bacteria multiply in the eyelid margin. Because these bacteria are not necessarily transferred from one person to another, some investigators consider a sty to be noncontagious. Others, however, feel that if another person contacts the causative bacterium and they touched their eyes, it is possible to transfer the infection, but this happens very infrequently; nonetheless, these experts consider this to be a contagious disease. The compromise position would be that, in most instances, a sty is not contagious unless certain circumstances are met, such as touching a sty and then transferring the causative organism to another person, where it may or may not cause a sty or other infection to develop.

How will I know if I have a sty?

Most people know when they develop a sty because of the symptoms and signs that are as follows:

  • A red lump or bump begins to occur on an eyelid margin that resembles a boil or a pimple.
  • Almost always there will be eyelid discomfort or pain.
  • Some individuals will develop eyelid swelling.
  • Some individuals will have increased tear formation.

Sometimes a sty is confused with a chalazion, which is a blockage of a small oil gland behind the eyelashes. It differs from a sty because it is usually not painful and is most prominent on the inner side of the eyelid. However, the treatment for both conditions is essentially the same.

Most doctors diagnose a sty simply by observation; no tests are needed.

Medically Reviewed by a Doctor on 3/9/2017

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