[CorkyMax]

Found this on net while searching for something else:

How Your Dog Reacts To Pain
All pain-relieving dog medicines are called analgesics. Pain perception depends partially on species, breed, age, gender, time of day, and your dog's individual temperament. Young dogs tend to have a lower threshold to pain. Older and debilitated dogs with health problems may not show as much response to pain - but they feel it just the same. Hunting and working breeds of dogs are more resistant to expressing their pain than toy or miniature breeds. When you take your dog in to an animal hospital, your dog is usually worrying about the visit and strange environment, and will often ignore the pain that you noticed at home.

Pain may lead to over-grooming the area that is painful. This can lead to hair loss and self-mutilation of the area. Some dogs tremble and move with their stomachs tensed up. Others tremble all over. Some will show lameness of an affected leg, while other dogs become aggressive, pant or grimace.

Any sudden behavior change in your dog can be a symptom of pain. Excessive salivation, licking of the lips, dilation of the eyes, rapid breathing and increased heart rate may all be attributable to pain. Some dogs in pain also eat less. Some become restless and do not sleep well. Some dogs stop grooming and appear dejected and depressed. Pain can cause an increase in body temperature, respiration, heart rate, and blood pressure.

Pain alone can actually change the results of blood chemistry analysis. Dogs in pain may have elevated blood sugar. Their blood cortisol and white cell levels often increase. Pain can also interfere with the immune system, increasing the risk of infections, and slowing the healing of wounds and surgical incisions.

[Todd]

thanks for sharing. important to understand when your dog is in pain because dog's have different ways of expressing it then us humans do. They try to hide it at times.