I used to get the chemical taste in the mouth and throat a lot. Now I only get it occassionally. I have since read that this is a side effect of certain medications - they impair our sense of smell, taste and even hearing.

This is very interesting- and sounds only too familiar: :( :(
A person who posted this was wondering if her asthma medication Advair was responsible for the following symptoms:

Prior to starting the drug-no symptoms
First week: loss of voice, thick phlegm, loss of gag reflex, pulling and itching in the throat
Breathing worsens
At two months: thick phlegm, ripping feeling at the back of throat, sinusitis-post nasal drip, dryness of mouth, constant loss of gag reflex, pain and aching in the throat, breathing problems

At 9 months: pulling, pushing at the back of the throat, acidic taste plus taste of food throughout the day, popping and gurgling of esophagus, uncontrollable burping, pain in the lungs, constant trouble breathing, dry mouth, dry throat, constant scratching painful feeling at the back of throat, barber wire feeling at the back of mouth, severe problems sleeping....

Diagnosis from seven doctors after many tests...unknown. Some of the more likely conditions were ruled out.