T.B.
My 4yo ds has been one big runny booger since he was a baby, until I took him to an ENT for a whole different problem. The ENT took one look at him, asked about his continuous runny nose, felt his neck, looked in this throat and dx'd him with over active tonsils and adenoids.
Ds had a tonsil/adenoidectomy done in May and he has been booger free since!! For years and years I'd thought he had allergies, but I was waiting to take him to an allergist when he was 4.
So, my point is, that not all continuous boogies are a result from allergies. If you can hold out and give Children's Claritin for a while, I'd take him in at 3.5 and see if he also has the same problem. My ENT said that it's very common for parents and pediatricians to write off continuous runny noses to allergies, but they're actually due to a problem with their tonsils/adenoids.