Immune defenses responding to a false alarm & Inhaled, swallowed, and injected allergens

Immune defenses responding to a false alarm

An allergy occurs when immune defenses react to a substance that does not trouble most people. Instead of responding only to harmful germs, the system responds to a false alarm. Genes and environment probably both influence susceptibility. A person may react to more than one substance. This mechanism explains why an ordinary exposure causes symptoms in one person but not another and why allergy is not the same as an infection.

Inhaled, swallowed, and injected allergens

Pollen, dust mites, mold spores, and animal dander are common allergens. Foods, medicines, and insect stings can also trigger reactions. Allergy is therefore not restricted to outdoor pollen or seasonal nasal symptoms. The relevant trigger differs between people, and practical avoidance depends on the specific exposure. Avoiding a food or medicine is a different task from reducing inhaled pollen or preventing contact with an insect sting.

Key concepts

Immune defenses responding to a false alarm

An allergy occurs when immune defenses react to a substance that does not trouble most people.

Inhaled, swallowed, and injected allergens

Pollen, dust mites, mold spores, and animal dander are common allergens.

Symptoms and anaphylaxis

Reactions may cause sneezing, runny nose, itching, rash, or swelling and may involve asthma or other breathing problems.

Testing and trigger-based management

Skin and blood tests help investigate which substances may cause reactions.

References

• MedlinePlus en español — Allergies and Immune Reactions