An internal sty causes a red, painful swelling, but its location prevents the pus from appearing on the eyelid. A stye develops rapidly, producing an elevated, painful, red, swollen area on the eyelid.
Most chalazia develop further from the eyelid edge than styes. A sty is a bacterial infection that appears as a small bump along the edge of the eyelid. A sty resembles a pimple and is located at the edge of the eyelids. Chalazions usually occur farther from the edge of the eyelid than styes, and tend to “point” toward the nose side of the eyelid.
If the eyelash stye lasts for more than 3 days or the infection appears to be spreading, consult an eye doctor. A sty is an infection of one of the follicles from which the eyelashes grow. A problem that can occur along with, or be mistaken for, a stye is an inflammation or infection of the eyelid (blepharitis).
Discharge from the infection causes the well known symptoms of eyelids stuck together on wakening or having a “crusty” appearance. Your eye doctor may recommend replacing your contact lenses after the stye has healed to prevent recurrence or spread of the infection.