An irritant is a compound that causes irritation. It can be dust, soot, and mildew. If you come into a building and start sneezing or your eyes begin to water, they are signs you may have been exposed to an irritant.
Another common irritant is pollen. Our pets often react to grass seeds. For most pets, grass seeds in the house can cause an allergic reaction. Grass seeds attach themselves to pets and cause inflammation. They can also enter the nose, ears, and mouths leading to unnecessary vet visits.