allergen

noun allergen

• dander — small particles or scales of hair or feathers
• irritant — tending to cause irritation; irritating.
• pollen — the fertilizing element of flowering plants, consisting of fine, powdery, yellowish grains or spores, sometimes in masses.
• antigen — An antigen is a substance that helps the production of antibodies.
• ragweed — any of the composite plants of the genus Ambrosia, the airborne pollen of which is the most prevalent cause of autumnal hay fever, as the common North American species, A. trifida (great ragweed or giant ragweed) and A. artemisiifolia.