What does erythema of the external canal refer to?

Erythema of the external canal specifically refers to the redness that occurs in the outer ear canal. This condition is often indicative of inflammation or irritation, which could be due to various factors such as infection, allergic reaction, or trauma. The term "erythema" is a medical descriptor used to characterize redness resulting from increased blood flow to the affected area, highlighting that there is an underlying issue causing this change in appearance.

In the context of the other options, swelling of the ear drum pertains to changes in the tympanic membrane, which is not directly related to the external canal. Fluid build-up in the ear typically describes a condition more associated with the middle ear rather than the external canal, and infection of the inner ear concerns entirely different structures and symptoms. Therefore, the focus on the outer ear canal for erythema confirms that this is the correct understanding of the term in question.