Indeed this is a common symptom of allergy.
However, when I spit it out, I find that some of it strangely looks like young candida threads.

In order to address this specifically, you will need to boost your immune system: echinacae or Rei shi mushroom will help. I find it helpful to boost the immune system, although it remains that this is a very basic symptom of candida and it will vanish on its own once you are cured.

I also find that when I do a bowel cleanse, I get more mucus coming out from my throat backdrop. Bowels and sinus are really closely related.

Jhan

Cheers,
Jhan

The mucus at the back of your throat is post nasal drip. Your sinus is dripping and running down into your thoat, picking up bacteria along the way and causeing the mucus to thicken. The best way to treat this is to get your sinus cleared up.

There are tons of ways to do this, but I use "Oxynasal Wash" from Dr. Donsbach, which can be found at http://www.oxygentherapies.com This stuff works instantly and I find it inexpensive. It has been a life saver for me because my PND always caused choking which was quite embarassing.

Aluna