But unlike an allergy and a sensitivity, which are blood - borne responses, an intolerance is a digestive system reaction to irritating foods. (dietselfhelp.com)
These substances can cause immune system reactions, particularly heavy metals like mercury. (dogsnaturallymagazine.com)
Excessive salivation is another autonomic nervous system reaction when the fight or flight instinct is triggered in dogs. (ka-hi.com)