Just like people, dogs are constantly exposed to, and threatened by, viruses, bacteria, fungi, foreign proteins, diseases, and more... and, just like your immune system, your dog's immune system is the natural defense against all these threats.
A healthy immune system has two components, (1)discrimination, which distinguishes your pet’s own normal organisms from dangerous invaders, and (2)recognition, which detects foreign organisms through the lymph nodes.
Once a foreign body is recognized a natural reactions begins, warding off the threat. This takes time, however, and first-time invaders sometimes produce illness. Severity depends on exposure and seriousness of the foreign agent. If firs