if itchiness existed for a long or apparently infinite time, this could be allergic conjunctivitis and atopic conjunctivitis (AKC)).
If eyes burn or tear or if there is a foreign body sensation, itchy eyes could be symptoms of dry eyes and/or Meibomian Gland Dysfunction (MGD), alsk known as posterior blepharitis, the most common form of lid margin disease.
Other important factors to consider are eczema and skin rashes, swollen eyelids, dots or hyperpigmentation, asthma, allergic rhinitis, contact lenses, redness of the eye, exposure to dust, pet dander, pollen or other allergens and the weather.
It's best to find out the cause of itchy eyes before looking for the solution. For instant relief of eye allergies apply a cold compress.