Benadryl and Reactive Airways Disease 21 month old

Is it OK to give a toddler benedryl at night to help with the constant post nasal drip if he has reactive airway disease?  Does this restrict the cough and make it worse?  He had a very bad reaction to singular...I feel terrible for him, he is unable to sleep with he gets this drip...

[allmymarbles]

Have you tried using saline in his nose? Take a ball of cotton, saturate it with a salt solution, place it at his nostril and squeeze. That will help clear the passageway. B5 is an excellent mucus thinner and I take it, but I do not know what dosage would be correct for so young a child.

As for Benadryl, antihistamines are drying. I should think that might make the condition worse, although it would help him sleep.

[Munch1969]

Thank you!  The doc recommended xyrex...he has absolutely no systems during the day, as a matter of fact, he takes a 3 hour nap during the day with no problem!  It is when the night time hits! He doesn't have a runny nose at all at night--just a post nasal drip which produces a cough-and also first thing in the AM when he wakes up--when he does get some sleep.  

[allmymarbles]

Do you mean Zyrtec? If so, that is a long-lasting anti-histamine. If I were you I would still try the saline. There is no harm in it. Even I use it and an anti-histamine does not work for me for post-nasal drip.