An allergen is a substance capable of triggering an allergic immune response in a person who is sensitized to it.
Common allergens include proteins from foods, pollens, dust mites, animal allergens, and some medicines or substances encountered in the environment.
Exposure to an allergen does not necessarily cause symptoms in everyone. An allergic reaction occurs when the immune system of a sensitized person responds inappropriately to the substance.
QUICK FACT
An allergen is not inherently harmful to everyone; what makes it an allergen is its ability to trigger an allergic response in susceptible people.
COMMONLY CONFUSED WITH
- Antigen: a substance or molecular structure specifically recognized by immune components; allergens are a subset of antigens.
- Irritant: a substance that can directly damage or irritate tissue without requiring an allergic immune response.
SEE ALSO