D.B.
COnjunctivitis is usually connected with a cold - the child gets germs on his hands, rubs his eyes, and bingo - infection. It could be viral or bacterial. It could also be an allergy. No one else is getting it, but you are being very vigilant to wash everything.
You're tried all the remedies, but those are after the fact. Have you considered prevention? A children's nutritional product that supports the immune system would make sense. The top product out there is Reliv. I would be happy to give you more info. No kids that I know get conjunctivitis, flu or strep if they are on Reliv. It's patented, and completely safe - no warning labels on anything, which you can't say about even kiddie vitamins. It's from a fine and honored company, and it's the sensible and successful way to go!