All allergy meds, prescription or over the counter, will affect each person differently.
So keep that in mind.
How old is your son????
I have general allergies to the air/dust, etc. Thus, I have tried many allergy meds.
I personally, do NOT like Zyrtec. Why? It makes me.... IRRITABLE and tired. I hate it. I really do not like Zyrtec for that reason, and I am an adult.
It also made my friend's son that way.
Each person, is different.
Now, Nasonex, is a type of steroid. My understanding is, that it should not be used forever. I have one sitting on my shelf right now. My Doc said only to use it if I have to. It is a steroid... therefore... it helps by decreasing INFLAMMATION. Which, per allergies, it causes an inflammation in the nose. Hence, stuffiness. It does not cure, the allergy. Just the stuffiness and nasal inflammation.
And it is for kids, after 2 years old.
You should get more information about Nasonex too.
Now, Singulair... can cause Behavioral issues. So know that. Personally, I would not give that to my kids. There are MANY other things that can be used. The Doc telling you she has never heard of these behavioral side effects, is very ignorant. I would not listen to her.
For me: I like Claritin. They have a kids version too. And you can get it over the counter.
Really, per allergies or seasonal allergies, it can be affected by the general air quality in your city too.
I would ALSO recommend, getting an air purifier for your home or for his room, or an air filter. My parents got some for our home when I was a kid. For that reason.
THEN.... you can also use a "Neti Pot" for your son. I don't know what his age is, but my daughter even at 3 years old, could use it with my Husband's help. It helps to clear up the nose/sinuses.
I really, would not use too many things at one time.
There is also: Allegra. Over the counter too.
OR, you can try "Little Noses" (in lieu of Nasonex. Which is a nasal decongestant, for kids. Over the counter. And it works. I have used this for my kids.
Here is the link for it:
http://littleremedies.com/
http://littleremedies.com/products/little_noses/decongest...
Or even just use a saline nose spray.
Over the counter.
This works real well too. And it is just saline nose spray.
I personally have: Asthma and allergies to things in the air. And, I only take my meds, when/if I have to. Not everyday. Per myself, I know which ones work for me the best.