An allergy is a hypersensitive, abnormal immune system reaction to a normal, usually harmless substance known as an allergen.
Medical Definition and Mechanism
- Altered Reactivity: Medically defined as an exaggerated or pathological immune response to an antigen (the allergen) following prior sensitization or exposure. Like a bee sting, the second sting reaction is usually worse.
- Antibody Production (IgE): Upon first exposure, the immune system mistakenly identifies a harmless substance as a dangerous invader and produces high levels of Immunoglobulin E (IgE) antibodies. This is what is measured in blood allergy testing by Heska.
- Chemical Release: On subsequent exposures, these IgE antibodies bind to mast cells and basophils, triggering the release of potent inflammatory chemicals—most notably histamine—which cause tissue swelling, itching, and redness.
So, basically, if an allergy is taking place you will have redness from a release of histamine. NO redness, NO allergy.
Many dogs and cats come into the clinic for itchy skin issues, most owners assume allergies are to blame but there can be other causes or concomitant issues.
Other causes of itchy skin:
1) Bacterial or fungal (yeast) infections
2) Ectoparasites, fleas, mites, lice, etc
3) Dry skin or unhealthy skin (EFA deficiency)
4) Contact irritants, bedding, shampoos, lawn sprays, shock collars, etc.
5) Nerve issues causing dermatome sensations.
