When a particle is going to cause an allergy in a dog, it is usually because it touches its skin or is inhaled for the first time and causes the body to produce antibodies. This is a normal reaction of the body against viruses, but in the case of dog allergies, this reaction is against normally inert particles that the body might accidentally consider to be a danger. In the case of dog allergy anti bodies chemicals that the dogs body creates are called IgE (immunoglobulin E).
This IgE antibody attaches to the allergen (particle of pollen, dust, food, grass etc) to “neutralize” it, just like IgG and IgM do to a parvo virus – which is a genuine threat to the dog of course. It is the process of the IgE attaching to an invader particle that begins a sensitization. This sensitization is a NORMAL human or dog response for the first TIME a dog encounters a allergen (or potential allergen). But it is the future reaction or massive over reaction that is the cause of the dog allergy and resltant suffering.
Without sensitization there would be no allergy. But without sensitization, there would be no immune defense as rapid responders – which are required to get infections under control before they grow out of control.
This type of allergy is the most common type, and is called atopy or atopic dermatitis.
The next time your dog is exposed to allergens such as dust particles they might suffer atopic dermatitis (an allergic skin condition). This is because their dog immune system mistakenly produces MASSIVE amounts of IgE antibodies very early on to the new season exposure. But unlike immune responses to viruses that are beneficial, this overkill can become debilitating to dogs and lead to secondary infections from bacteria and fungus.
Why overproduction of IgE leads to inflammation and dog scratching
Once the IgE chemical has attached to the allergens in the blood, it then attaches to a cell called a MAST cell. The Mast cell is also called a mastocyte or a labrocyte and is created from the myeloid stem cell. Mast cells contain the chemicals that cause inflammation (in certain over sensitive dogs). The main chemical that every human hay fever sufferer is aware of is called Histamine.
When an IgE antibody, with attached allergen, finds a mast cell under the dog skin, it alters the membrane of the Mast cell, and the histamine chemical leaks into the surrounding tissue causing inflammation. The physical sign of the histamine reaction of the dog’s skin is seen as redness (erythema) and the resulting severe dog itchiness (pruritis) occurs on the skin surface. The overall reaction is called a wheal or a hive(s).
NOTE that in flea allergies (one of the main other dog allergy reactions) it is the dog allergy reaction to the flea saliva rather than the mast cell issue that causes itchiness.
Atopy is of course not as simple as all this. Other chemicals that affect nerve fibers to the skin and cause extreme itches are: cytokines, leukotrienes, neuropeptides, peptides, proteases, and Interleukin 31 (IL-31) are also involved.
The IgE antibody. allergen and mast cell histamine leakage CAN causes atopy in both air-borne allergens and food allergens. However another physiology is often at work when it comes to food allergies (see future articles on this site specifically about food allergies) – in the case of FOOD the allergen is usually not an inert particle like pollen but a meat of vegetable protein reaction.
For food sensitivities it is the protein being absorbed through the lining of the small intestines and into the blood that causes the reaction. In theory the stomach should have broken the protein down into amino acids then further into blocks for energy or building other proteins or structures in the body, but some protein that doesn’t get used can cause these allergy reactions too. Severe food allergies in dogs can cause the same symptoms as humans get such as IBD (inflammatory bowel disease).
While the complete body reaction gets very complicated and may require a medical degree to fully understand it (well as much as humans have discovered so far) for the purposes of this site, understanding why it is occurring at a macro level and how to prevent it, or neutralize the affects is more relevant to most dog owners. That is what we will provide in other articles on this site.