My Dog Has A Sore On The Side Of His Anus, That Is Not Healing. What Could It Be?

Dogs have anal glands--they are scent glands located at 4 and 8 o'clock around the anus.  These gland produce a smelly liquid that they should express when they defecate.  These glands can become impacted with a thick, pasty material and then become infected.  Infected anal glands can rupture though the skin leading to a draining tract.  When they rupture blood, pus, and anal gland discharge may be present. 
Other wounds or cuts could be the problem.  A mass that ulcerated and is now bleeding is possible.
Your dog needs to be examined by a veterinarian to determine the cause, then placed on appropriate medication.  You need to prevent him from licking by having him wear an Elizabethan Collar.  It will never heal even on antibiotics if your dog constantly licks and chews the wound.
When a dog's anal glands are full they often lick their anus and "scoot" across the floor.  These are signs they need to be expressed.  This can be done by your veterinarian or you can learn to do it yourself (your vet will show you).

I agree with the first comment. My Newfoundland had the same problem. Twice a year he had to go into the vet to have his anal sac expresses because it did not drain properly when he pooped.  It was unpleasent for him, but it was like a prostate exam/pimple pop in one manuver. But it's not a serious medical problem, or an expensive one. Pets get strange ailments same as us humans. The signal my pup needed a vet appointment was when he paid too much grooming attention to his bum or tried to drag his butt across the rug. Good luck!

This sounds very much as if he has burst an anal gland abscess.  He really needs antibiotics.  I also recommend that you keep the area as clean as you can with either salty water, or a suitable antiseptic solution.  Be careful, as these abscesses are very germ-ridden, and also very sore for the dog.

He could of gotten bitten by a Bot Fly, and their larvae or eggs imbeds themselves inside the dog, cause a red/pink irritated hard spot.  It can make them very sick, if it is not lanced and the larvae is not removed.  It is very common in the south and other areas throughout the United States as well.   Good-Luck!!!

Dogs usually bite themselves on the areas where they feel sever itch. It is possible that he might got an insect bite or contact allergy which caused itch. This itching by mouth lead to infection. My suggestion is to take him to Vit and get proper diagnosis of the problem and then start treatment. Don't try to treat by yourself because it can cause some complications.

Is your dog male or female?  If female, is it possible she's either in heat, or become pregnant and had a miscarriage? She may have an infection from incomplete miscarriage.

Whether your dog is male or female, I agree with vampfreak, as to the possibility of a blockage of some sort.

While dogs and cats can occasionally have blood in their faeces once in a blue moon, and then it's gone again,  the fact it smells is the part that causes concern and, could indicate infection and really, a trip to the vets is probably necessary to make sure it requires nothing more than a course of antibiotics. If there is a blockage, your vet can discuss treatment options.  For your own peace of mind and in the dogs best interests, make an appointment.

All the best.

Probably impacted anal glands leading to scratching and dragging the bottom along the ground. Get it to the vet for the glands to be emptied- a quick, easy procedure but very very smelly and gross..

Yes it could be the result of self trauma from sore impacted anal glands or irritation from flea allergies, or it could be a dermal condition of the skin around the anus itself.  Go along for a vet check.

Your dog might have a sensitive digestive system that got irritated. The blood should stop within a few days. He could also have a blockage. So call your local vet and talk to them, they can help you