I have a 7 year female red tail boa.  (She was sold as a red tail boa although she looks to me more like a boa constrictor imperator. I also read they are commonly sold as red tails.) Her name is Lillith.

About 2 weeks ago, I had her out of her tank.  I noticed she had blood dripping out of her mouth when she stuck her tongue out.  I held a tissue to her mouth for about 3 minutes and the bleeding stopped.  I immediately made a vet appointment and we went in the next day. 

The vet found no problems with her.  She has good muscle tone and her scales looked good.  The vet opened her mouth and found no signs of infection, swelling, redness or cuts.  The vet could find nothing wrong with Lillie from an external examination.  So she said for me to just keep an eye on Lillie for other symptoms.  

I also told the vet that Lillie had not eaten since 1/1/12.  She said it can be normal and to just wait a few weeks and try feeding again.  She normally eats frozen jumbo rats, but  I picked up a large rat and a large mouse to try feeding next time.  I tried feeding on 2/1, 2/15 and 3/4.  She shows no interest in eating.  I even tried feeding her in her container.

Tonight, she started drooling.  She had been out of her tank for about 20 minutes and she had a thick clear liquid coming out of the sides of her mouth.  It was so strange I decided to look it up.  I read it can be a sign of a respiratory infection.  The vet will be closed until Monday.  I will give a call on Monday to run this by the vet, but I would really appreciate some community advice. :)

In a nut shell:

2 weeks ago - bleeding from the mouth

2 months, 10 days no eating

Drooling clear viscous liquid from sides of her mouth.