Bloodshot eyes and allergies: what to know

Allergens such as dust, pollen, mould or animal dander can trigger inflammation of the conjunctiva, the clear lining over the white of the eye. Itching is a strong clue, and symptoms commonly affect both eyes. Sneezing or a runny nose may occur at the same time.

Allergic conjunctivitis does not spread from person to person. A gritty feeling, sticky discharge, eyelid swelling or symptoms beginning in one eye can also fit conjunctivitis or another eye problem, so redness should be judged alongside the other symptoms.

Avoid the suspected trigger, keep windows closed when outdoor pollen is high, and rinse the face after exposure. A cool clean compress can ease itching. Do not rub the eyes, because rubbing can increase swelling and surface irritation. Ask a pharmacist or clinician which allergy drops are appropriate, particularly if you wear contacts.

Get prompt medical advice for eye pain, blurred or reduced vision, strong light sensitivity, a marked one-sided redness, or swelling that is worsening. Seek emergency help for sudden vision loss, severe swelling with breathing difficulty, or a chemical splash; rinse the eye with clean water while obtaining help.

Ask which trigger is most likely, whether an allergy treatment is suitable for your eyes, and how to distinguish allergy from infection. Tell the clinician about contact lens use, new cosmetics, medicines, and any discharge.