While conjunctivitis that is not triggered by allergies often affects only one eye, allergic conjunctivitis usually affects both eyes at the same time. Allergic conjunctivitis also tends to affect both eyes equally, though one eye sometimes is afflicted more severely than the other.

The primary symptom of allergic conjunctivitis is itchy eyes. The surface of the eyeball also takes on a puffy appearance, though vision usually remains unimpaired. The conjunctiva (the mucous membrane covering the white of the eye and inside of the eyelids) reddens and there is a large amount of watery discharge. Allergic conjunctivitis sometimes spreads to the eyelids, which may become red, dry or scaly.

Signs and symptoms of allergic conjunctivitis will vary, but may include:

• Mild eyelid swelling
• Itching and burning
• Tearing of the eye
• Dilated vessels in the conjunctiva
• Watery or stringy mucus-like discharge
• Eye redness
• Sensitivity to light (photosensitivity)
• Occasional blurred vision
• Allergic shiners (darkening under the eyes)
• Bumps on the inside of the eyelids
• Sleep difficulties

Though allergic conjunctivitis can appear on its own, it usually is associated with allergic rhinitis. However, a person who has itchy eyes, tearing of the eye or other symptoms does not necessarily have allergic conjunctivitis.