A deviated septum, which occurs when the nasal septum (the wall between the nostrils) is crooked or damaged, can make it difficult for the body to drain mucus correctly. This may cause postnasal drip. Post nasal drip, if infective and not just allergy-related, can cause bad breath. Bacterial and viral sinus infections have particular odors associated with them depending on the bug. The clear. I have post nasal drip and dr thinks i am alergic to dusts mites. recommended singular, but I don't like taking it. Is zyrtec or claritin a good alternative Sinus infections can cause stuffiness of the nose with nasal blockage, which can make breathing through the nose difficult. It can also cause post nasal drip and lead to an irritation in the throat. Is Claritin helpful for Chronic Post Nasal Drip? can Claritin cause Chronic Post Nasal Drip? Claritin is mentioned in 854 posts about Chronic Post Nasal Drip. Post-nasal drip is what happens when the sinuses make so much mucus that the mucus runs down the back of your throat, and it can cause a chronic cough known as upper airway cough syndrome (UACS). This is a case of double insult to injury: Sinus infections can both cause and be caused by post-nasal drip! The caused by part comes in when post-nasal drip prevents your sinuses from draining properly. Claritin can treat post-nasal drip caused by sinusitis and viral infections, according to WebMD. Post-nasal drips are caused by a variety of conditions, and the method of treatment depends on the underlying cause of the post-nasal drip.