Mites that cause Terrible Allergies

Mites that cause Terrible Allergies

By Dr. Ed Mapes
Stonebridge Animal Hospital
McKinney, Tx

Dust mites and storage mites – who knew they could cause so much itching? Cases of allergic dermatitis have been unusually severe recently, and we have performed quite a few allergy tests over the last few months.

The most common allergens (substances to which animals have allergic reactions and dermatitis) are proving to be Dermatophagoides farinae (the house dust mite) and Tyrophagus putrescentiae (storage mites). Even patients that react positively to other things, like grasses or tree pollen, often react to these mites as well.

House dust mites live in the home – in carpets, bedding, mattresses, upholstery and cloth toys; even in immaculately maintained homes. They exist on organic debris like human skin cells and hair follicles, bacteria, fungi and viruses in the environment. The mites have digestive enzymes that are released in their feces and are major inducers of allergic reactions.

Storage mites are present in dry foods, cereals, grains, straw and cheese— all substances that can get moldy. Once introduced into the home, however, storage mites actually live in conjunction with house dust mites, and occupy the same areas.

House dust mites and storage mites are present in the home throughout the year, and will cause non-seasonal (year-round) symptoms of allergy including itch, redness of the skin, and recurrent otitis in dogs and cats. The itch is strongest on the feet, face, and ears, but can reach all parts of the body.

Allergies begin when the immune system misinterprets proteins from the mites as a disease agent, and produces antibody to counteract the agent. This antibody, called IgE, binds to mast cells in the skin and to white blood cells called basophils. The mast cells and basophils release substances that cause inflammation and the symptoms of allergy whenever the animal encounters the allergen again. This is on a daily basis when the mites are right in the home environment.

Ridding the home of these mites is literally impossible; unless you seal the building, filter the air, never open a door or window, never leave the home, and have all groceries scanned before entry!

The allergic reactions to these mites tend to be very strong, and treating with medications such as antihistamines, corticosteroids, or omega fatty acids is usually insufficient to stop the itch. The best treatment is hyposensitization, also called “allergy shots” in human medicine.

The treatment consists of either injections or orally-administered immune serum that causes production of a different antibody, IgG. This IgG competes with IgE on the surface of basophils and mast cells, and interrupts the allergic reaction.

This therapy is very effective in roughly 85% of cases, meaning that symptoms are controlled without giving other medications. Many of these patients get to experience life without the constant itch for the first time in months or years. Some patients have break through episodes and receive medications on a short term basis to alleviate symptoms, while a very few animals fail to respond satisfactorily to the therapy and still require maintenance medications.

Comments are closed.