Hi MK!
I would encourage you, if you are able, to stop suctioning his nose (not effective and can be too rough on the nasal passages) and rinse it instead. This is quite the scary undertaking if you've never done it before, but I've done it with my two girls since they were babies, and they do great! You can either make your own solution and use a short tip suction bulb to squirt it or you can check out products here to see if they may be a fit:
http://www.sinucleanse.com/
My homemade nasal rinse solution is:
2 cups filtered water
1 tsp. sea salt
1/2 tsp. baking soda
Also, I am in Denton, and we have a great local naturopath at Nature's Remedy: http://naturesremedydenton.com/
She recommended ALJ made by Nature's Sunshine for my daughter's allergies. My daughter had been on Zyrtec nonstop since 9 months old, and it was ineffective during seasonal flairups. With the ALJ she is 100% off Zyrtec and doing great despite having allergies to grass. You can also call up there and ask the woman any other recommendations she has...
You may also want to look into underlying allergy causes (in food eaten). Pastuerized, Homogenized Dairy is the #1 offender of allergies in America (where is raw milk from pastured cows is not for most people). Also, grains introduced too early in a child's life can lead to allergies later on...I have heard a lot of people utilizing the GAPS diet successfully to heal allergy issues.
Don't know if you can get your kid to take this, but Olive Leaf Extract is an EXCELLENT anti-viral and anti-biotic!
Hope this helps!
God's Grace to you,
Lisa :)