How to prevent crusty eyes when having a hay fever?

Eye drops: Assuming that your symptoms are truly 'hay fever' - i.e., due to allergy, antihistamine eye drops will be the most helpful. You should see your primary care physician or allergist for this, though. Most otc eyedrops have a decongestant in them to "get the red out" - these can cause irritation if used frequently; this is not a problem with prescription drops.