-- Question: My allergies cause my eyes to water and itch. Can I damage my eyes by rubbing them too much?
Answer: Rubbing your eyes won't help your itch at all. As a matter of fact, it will make the itching worse over time.
Now, it also causes more inflammation to your eyes. Once you have more inflammation you have more irritation, you'll get something called reflex tearing which explains the tearing you see with bad allergic conjunctivitis.
Now if the rubbing of your eyes goes on for some period of time, there's some studies that indicate that maybe you could develop thinning of the cornea -- a condition that's called keratoconus. If it becomes very severe, it may even require a corneal transplant.
So try to avoid rubbing your eyes; it could cause harm.