What is the cause of these itchy eyes symptoms? No pus in the eyes.

Allergy. Allergy and dry eye are the most common. Blepharitis too, but often is associated with crusting. Go to ophthalmologist and get a prescription for pataday/bepreve- very helpful. Try artificial tears first.
Many possible causes. 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.