What is the best way to relieve itchy eyes?

Eyedrops: I would get some otc allergy eydrops and use as directed. If these don't help than prescription drops can be prescribed. Taking systemic anti-histamine generally are not effective for eye allergies.

Depends on the cause: There are many causes of itchy eyes. Several types of inflammatory conditions, allergic reactions, detergents, chemicals, and sometimes bacterial, viral or fungal infections can cause itchy eyes. Have it evaluated by a professional and get the appropriate treatment.