allergen

noun

al·​ler·​gen ˈa-lər-jən 

: a substance (such as pollen) that induces allergy

allergenic

ˌa-lər-ˈje-nik 

adjective

allergenicity

ˌa-lər-jə-ˈni-sə-tē 

noun

Examples of allergen in a Sentence

common allergens, such as pollen

Recent Examples on the Web

This keeps the area sanitized and removes any mold or allergens that can become a problem if they’re left untouched. — Ashlyn Needham, Southern Living, 4 Aug. 2026

One study published in the World Allergy Organization Journal found that cow's milk is one of the most common allergens among children. — ABC News, 3 Aug. 2026

The formulas are backed by experts in microbiome science and dermatology, and are free from preservatives, allergens and unnecessary ingredients, such as oils, that could irritate the skin. — Samantha Conti, Footwear News, 31 July 2026

Per Lidl, the cookies sold under the company’s Eridanous brand contain undeclared allergens, including wheat, soy, milk and egg. — Saleen Martin, USA Today, 29 July 2026

Word History

Etymology

borrowed from German Allergen,, blend of allerg- (in Allergie allergy) and -gen (in Antigen antigen)

Note: See note at allergy.

First Known Use

circa 1907, in the meaning defined above

Kids Definition

allergen

noun

al·​ler·​gen ˈal-ər-jən 

: a substance (as pollen) that causes allergy

allergenic

ˌal-ər-ˈjen-ik 

adjective

Medical Definition

allergen

noun

al·​ler·​gen ˈal-ər-jən 

: a substance that induces allergy

inhaled allergens

a suspected food allergen