What is the most common etiology of episcleritis?

• A. Bacterial infection
• B. Autoimmune disease
• C. Idiopathic
• D. Allergic reaction

Answer: (C)

The main idea is that episcleritis most often occurs without an identifiable underlying cause. In most patients, there’s no systemic disease or local trigger that explains the inflammation of the episcleral vessels, so it’s labeled idiopathic. Autoimmune diseases can be associated with episcleritis in some individuals, but those cases are less common overall. Bacterial infection and allergic reactions are not typical drivers of episcleritis; infections tend to present with signs of conjunctivitis or other ocular surface involvement, and allergies usually show itching and a different pattern of redness. So, the reason idiopathic is the best answer is that it accounts for the majority of episcleritis cases, with associations to systemic disease being possible but not the rule.