Which sign is used to identify brimonidine allergy?

• A. Injection in bottom 1/3 of eye
• B. Increased tearing
• C. Red eyelid swelling
• D. Dryness

Answer: (A)

Allergic reactions in the eye from a glaucoma drop tend to show conjunctival redness from a localized allergic response, often with involvement of the lower conjunctiva where the drop pools. The sign described as injection in the bottom third of the eye points directly to this conjunctival hyperemia pattern, which is a characteristic feature of brimonidine allergy. This makes it a clearer indicator of an immune-mediated reaction to the medication than the other symptoms, which are more nonspecific to irritation or dryness. Increased tearing can happen with many irritants, dryness is a general tear-film issue, and red eyelid swelling can occur with allergies too but is less specific to brimonidine in this context. So the lower-eye conjunctival injection best identifies brimonidine allergy.