Chalazia are enlargements of an oil gland (similar to a pimple) deep in the eyelid caused by an obstruction of the gland's opening. Styes are infected eyelash follicles.
A chalazion is inflamed but not infected. A stye is usually caused by a staphylococcal infection. Sometimes the person also has blepharitis (see Blepharitis). Some people may have one or two styes in a lifetime, but other people develop them repeatedly. Rarely, a stye develops in one of the deeper glands of the eyelid (an internal stye).
At first, a chalazion may cause a swollen eyelid, mild pain, and irritation. However, these symptoms disappear after a few days, leaving a round, painless swelling in the eyelid that grows slowly for the first week. Occasionally, the swelling continues to grow and may press on the eyeball and cause slight blurring. A red or gray area may develop on the underside of the eyelid.
A stye usually begins with redness, tenderness, and pain at the edge of the eyelid. Then a small, round, tender, swollen area forms. The eye may water, become sensitive to bright light, and feel as though something is in it (foreign body sensation). Usually, only a small area of the eyelid is swollen, but sometimes the entire eyelid swells. Often a tiny, yellowish spot develops at the center of the swollen area, usually at the edge of the eyelid. The stye tends to rupture after 2 to 4 days, releasing a small amount of material and ending the problem.
With an internal stye, pain and other symptoms are usually more severe than with an external stye. Pain, redness, and swelling tend to occur underneath the eyelid. Occasionally, inflammation is severe and may be accompanied by fever or chills.
A doctor bases the diagnosis on examination findings.
Most chalazions disappear without treatment within 2 to 8 weeks. If hot compresses are applied several times a day (for example, for 5 to 10 minutes 2 to 3 times a day), chalazions may disappear sooner. If chalazions remain after this time or if they cause vision changes, a doctor can drain them or inject a corticosteroid into them. Because chalazions are not caused by an infection, antibiotics are usually not effective.
Although antibiotics are sometimes used to treat styes, they usually do not help much, because styes tend to resolve within a few days even without them. The best treatment is to apply hot compresses. The warmth helps the stye come to a head, rupture, and spontaneously drain. Because an internal stye rarely ruptures by itself, a doctor may have to surgically drain it. Internal styes tend to recur.
Last full review/revision October 2014 by James Garrity, MD