The problem is that both the esophagus (to the stomach) and the trachea (to the lungs) start in the throat (pharynx). There is kind of a valve (glottis and epiglottis,and uvula, the funny little thing hanging down at the back of your throat) that closes off the pathway to the lungs when we are eating food.  But if this doesn't work probably (like when we gag on something, or it goes "down the wrong tube" and we have to cough up and re-swallow it - then food, saliva or stomach acid coming up the esophagus from the stomach, can get down the wrong tube into the lung.  This can cause (or is thought to contribute to) asthma and can also cause pneumonia, because germs in the food will be in the lungs.   This happened to the wife of someone I work with - she 'aspirated' (breathed in) fluid while sleeping and ended up with pneumonia.

It can also get into our Eustachian tubes and cause ear & sinus problems.  (The human body is a wonderful thing, but not guaranteed perfect!)  I have some of this problem, I think. I seemed to start acquiring allergies & sinus problems about the same time or a little before, I was diagnoses with reflux problems.

     I also had problems singing due to acid reflux affecting my vocal cords.  Now, I kind of use that to figure out if I'm refluxing:  If I can sing on a given day, I didn't have reflux the night before.  I sleep on a bed with the head raised, but sometimes due to my husband's snoring and leg movements, I move to another bed, which DOESN't have the head raised ... will have to do something about that!

    Hope this helps...   Beethoven lost his hearing in middle age, it is thought to be a result of some kind of infection problem between his digestion and his ears - maybe reflux, which about 50% of people over 50 have, according to what I've read (however, I am not an expert or a medical professional).