swollen eye

My six year old son was with me in the backyard and in a matter of minutes his eye swelled shut.
Assuming it was a grass allergy, he got some benadryl and went to sleep.  It has been 2 hrs and the swelling is reduced but not gone.  Any other ideas on what I can do to help him out.  I have washed and rinsed the eye numerous times and cannot see anything internal irritant inside the eye.

[John C Hagan III, MD, FACS, FAAO]

This is almost always a allergic contact reaction. You can try some cold compresses or ice on eyelids and bendaryl    should be oK tomorrow.

JCH MD