What Causes a Stye?
Styes (hordeola) are caused by bacterial infection of the eyelid oil glands, most commonly by Staphylococcus species. 1
Primary Causative Mechanism
- Bacterial infection is the fundamental cause, with Staphylococcus being the predominant pathogen 1
- The infection specifically targets the meibomian glands (internal hordeolum) within the tarsal plate of the eyelid 1
- Other bacterial species may occasionally be involved beyond Staphylococcus 1
How the Infection Develops
The pathophysiology follows a predictable sequence:
- Gland obstruction occurs first, creating a blocked oil gland that provides an ideal environment for bacterial overgrowth 1
- Bacteria proliferate within the obstructed gland 1
- The body's inflammatory response to the infection produces the characteristic redness, swelling, and pain 1
Key Risk Factors That Lead to Styes
Eyelid-Specific Factors
- Blepharitis (chronic eyelid margin inflammation) creates conditions favorable for stye formation 1
- Poor eyelid hygiene allows bacterial accumulation on eyelid margins 1
- Meibomian gland dysfunction with blockage of oil glands predisposes to infection 1
- Previous styes or chalazia increase recurrence risk 1
Behavioral and Environmental Factors
- Contact lens wear, particularly with poor hygiene or overnight wear 1, 2
- Eye makeup that blocks glands and harbors bacteria 1
- Contaminated eye products, including expired makeup or solutions 1
Systemic Medical Conditions
- Rosacea increases susceptibility 1
- Diabetes mellitus impairs immune response 1
- Immunosuppression from any cause 1
- Atopic dermatitis/blepharoconjunctivitis 1
Clinical Caveat
While external hordeola (styes) and internal hordeola share similar bacterial causes and risk factors, the distinction matters for treatment planning—internal hordeola affect deeper meibomian glands while external styes affect the glands of Zeis or Moll at the eyelid margin. 3, 4