noun, plural: allergens
An antigen that causes an allergic reaction in an organism.
The allergen can be acquired through ingestion, inhalation, injection, or contact with skin. Common allergens include pollen, spores, grasses, dust and certain medications.
Word origin: German Allergen : Aller(gie), allergy + -gen, -gen (from French -gène
Related forms: allergenic (adjective).
See also: allergy.