What causes 'throat clearing habit' in adults?

I agree that it is more likely she is clearing her throat out of habit rather than necessity. Did she have a cough/cold recently which may have triggered this response. She probably doesn't even know she is doing it so regularly. Does it really bother you?

You can just ask her if her throat is bothering her because you have noticed she seem to be clearing it a lot. Hopefully if you ask her in this manner you won't feel so awkward about it.

Maybe getting her some cough drops might help break the habit.

This sounds like Silent Reflux, lots about this on the web. but basically to do with  a lack of stomach acid. 

Yes, I understand, chronic clearing throat habit without any symptoms is more annoying for friends and family than the patient. Perhaps it is a vicious cycle. Once someone becomes used to clearing their throat, it can become more of a behavioural issue - i.e. the more they clear their throat; the more they will feel like they need to clear it. However, clearing throat for more than three months, can make the condition chronic and can gradually alter the voice.

Try lifestyle modification changes prior to medications, if there are no serious symptoms, you can observe. Keep head elevated 30 degrees or more. Do not drink or eat within 3 hours of lying down.

Luis

Last year, I constantly felt like I had this drip down the back of my throat, and I was always clearing my throat. I searched everywhere for the answer, but didn't find anything that helped. It took me nine months and many incorrect diagnosis to finally figure out. It wasn't silent reflux. It wasn't allergies. It wasn't a virus, or a bacteria. It wasn't just a habit.

In the end, it was something very simple and easy to solve. I had mild but chronic riboflavin deficiency.

Riboflavin, B2, is a water soluble vitamin that is needed every day, because you do not store more than a days supply in the body. Severe riboflavin deficiency is rare due to all the added riboflavin to bread and processed food. But mild riboflavin deficiency is common, and it can happen for lots of different reasons. When it does, your lips may get dry and chapped for a day or two. If you're lucky, that is all that will happen. But if it continues, your throat becomes dry and you feel every drip of mucus. You get this annoying tickle all the time.

Several of the B vitamins can actually cause this. And generally if you are deficient in one of the Bs, you are likely low in many of them because they all work together.

One clue to this problem being a riboflavin deficiency is if you also have dry eyes, or burning or itchy eyes. If you've been chronically low in B2, the whites of your eyes may have a lot of red veins.

A simple trip to the vitamin aisle for some high potency B2 (and a b-complex just to cover your bases) and you'll be on the road to recovery. It can take a week for complete improvement in your throat. Your eyes will feel better in minutes. Riboflavin is often prescribed for migraine sufferers as well.

Most of the B vitamins will affect the mouth and throat if you become even mildly low in them. I wish more doctors considered this as a possible cause. Maybe I would not have suffered so long. I had this problem for years. It probably started for me after some bad advice to avoid dairy products, one of the main sources of riboflavin in the diet. Many people are told to avoid dairy when they have nasal allergies, or mucus draining. But then you can have more problems if you are not getting enough riboflavin from somewhere else in your diet.