View Table of Contents
- Allergy facts
- Allergy overview
- What is an allergy?
- What is an allergy? (Continued)
- What causes allergies?
- What causes allergies? (Continued)
- Who is at risk for allergies and why?
- What are common allergic conditions and what are allergy symptoms and signs?
- Allergic rhinitis (hay fever)
- Allergic eyes (conjunctivitis)
- Eczema (atopic dermatitis)
- Hives (urticaria)
- Allergic shock (anaphylaxis)
- Where are allergens?
- In the Air We Breathe
- In What We Ingest
- Touching Our Skin
- Injected into Our Body
Where are allergens?
We have seen that allergens are special types of antigens that cause allergic reactions through the IgE antibody. Allergens may be inhaled, ingested (eaten or swallowed), applied to the skin, or injected into the body either as a medication or inadvertently by an insect sting. The symptoms and conditions that result depend largely on the route of entry and level of exposure to the allergens. The chemical structure of allergens affects the route of exposure. Airborne pollens, for example, tend to have little effect on the skin. They are easily inhaled and will thus cause more nasal and respiratory symptoms with limited skin symptoms. When allergens are swallowed or injected they may travel to other parts of the body and provoke symptoms that are remote from their point of entry. For example, allergens in foods may prompt the release of mediators in the skin and cause hives.
The specific protein structure is what determines the allergen's characteristics. Cat protein, Fel d 1, from the Felis domesticus (the domesticated cat), is the predominant cat allergen. Each allergen has a unique protein structure leading to its allergic characteristics.