FAQs about house dust mite and storage mite allergies

Because house dust mites and storage mites are microscopic, the general feeling about them among clients could be "How much harm can they cause my pet?"

In fact, the most common allergen in dogs and cats (and in people, too) is dust mites. Anyone who is allergic to dust mites can attest to the miserable symptoms this condition can cause. It seems our domestication of dogs and cats (i.e., bringing them into our households and beds) also succeeded in sensitizing them to this common allergen.

Here are answers to several frequently asked questions about house dust mite and storage mite allergies.

Where are dust mites found?

Dust mites (Dermatophagoides farinae, Dermatophagoides pteronyssinus) reside in textiles such as carpet, bedding, mattresses, upholstery and cloth toys. They prefer a specific temperature and humidity to flourish, which is easy to come by during periods of sleep. Mites have translucent bodies and prefer the dark, and they like a sleeping body that is exhaling warm, moist air.

Dust mites feed on human skin scales, bacteria, fungi and viruses in the environment. They prefer the skin scales of atopic individuals because their skin lipids differ from nonatopics (Photo 1). The actual source of the allergen is the protein Der p 1, which is found in dust mite feces.

Photo 1: Facial excoriation in an atopic cat that is dust mite allergic.

What are the signs of dust mite allergy in pets?

Such allergies tend to be nonseasonal, but they can peak in the spring and fall. In dogs, recurrent pyoderma, pruritus (generalized or involving the face and feet), recurrent otitis or seborrhea—i.e., all the usual signs of atopy—may be present (Photo 2).

Cats may show eosinophilic granuloma complex lesions, pruritus, chin acne, recurrent otitis or plasma cell pododermatitis (general signs of atopy).

Interestingly, 30 percent to 80 percent of atopic dogs and cats skin-test positive to dust mites. In my experience, some pets that formerly lived outside can become sensitized after a period of time once brought to live inside.

What's the best way to determine if an animal has dust mite allergy?

The history of signs in the pet should be one of nonseasonality, with food allergy and ectoparasites ruled out. The pet can then be tested either via skin or serum for an IgE reaction to dust mites. D. farinae is more common in the United States, while D. pteronyssinus is more common in the United Kingdom, but both species exist in both countries.

The pet's clinical signs are usually responsive to corticosteroids; however, this is not diagnostic. Dust mites are acarids and belong to the same order as Sarcoptes, Otodectes and Cheyletiella species mites and food storage mites. So they may cross-react with one another on skin testing—i.e., if a patient has scabies, it may have a false positive test result for dust mites.

What are the treatments for dust mite allergy?

Once it's been proven a pet has this allergy, immunotherapy (subcutaneous or sublingual), treatment with cyclosporine, corticosteroid administration and/or environmental treatment should be undertaken. Matthew Colloff (in Dust Mites, 2009)1 scientifically evaluated all the methods for environmental treatment of dust mites (avoidance is preferred but unlikely), with the best being airing out fabrics on a hot, sunny and dry day or a cold and dry day for 12 hours followed by vacuuming.

Advise clients to use microporous mattress covers and to wash bedding in hot water (> 122 F [50 C]) monthly or in cold water using tea tree oil. If possible, remove carpets from bedrooms. Vacuum weekly all carpets and upholstered furniture by using a HEPA-filter vacuum, or steam clean mattresses, animal bedding and upholstery.

The study found that air ionizers and chemical dust mite "killers" are not as effective. The only chemical agent that helped a little was benzyl benzoate, but it had to be used at four times the recommended amount and left on carpets for l2 hours before vacuuming.

Where are storage mites commonly found?

These particular mites (Tyrophagus putrescentiae, Lepidoglyphus destructor, Acarus siro) are present in dry foods, cereals, grains, straw and cheese—i.e., substances that can get moldy. Like dust mites, storage mites can cause nonseasonal signs, including pruritus, erythema and recurrent otitis in dogs and cats. They're well-known in humans for causing asthma and allergic rhinitis ("baker's lung").

Data have shown that storage mites live in conjunction with house dust mites and can be found in bedding, mattresses, upholstered furniture and fabrics. One study in humans found storage mites to have overtaken dust mites as a leading source of allergy.

A popular misconception is that storage mites are present in bags of food or cereals from the manufacturer. In one study, out of 10 bags of dry dog food, one was found to have storage mites, but the rest developed the mites after being in the owners' homes.2

What's the best way to prevent storage mite occupation of dry pet foods?

Advise clients who have allergic animals to buy dry pet food in small bags, immediately empty the bags into sealed bags and place them in a freezer. Keep one bag out in an airtight container and feed the pet from that bag first. Take the food that is next to be fed to the animal out of the freezer and place it in an air-tight container to thaw.

Canned food or a cooked diet that doesn't contain grains or cereals may be fed to the animal. For example, cooked hamburger is OK but not the bun; cooked oatmeal instead of Cheerios; cottage cheese instead of sliced cheese (since it doesn't mold as easily).

Keep in mind that it's unknown if microwaving or freezing dry food is sufficient enough to kill storage mites. The reason for freezing unused new food is to prevent the food from being contaminated with storage mites in our homes.

How is an allergy to storage mites diagnosed?

This allergy should be suspected if the problem is nonseasonal, especially with facial involvement (e.g., pruritus, recurrent otitis, asthma or waxy otitis). A cooked diet with no cereals, grains or cheese can be given for four to six weeks to see if the patient improves.

Perform skin or serum testing for various storage mites, but advise the client that mites cross-react on skin testing, and some animals may test positive for both dust mites and storage mites. Some of these patients will be allergic to both, while others will be allergic only to one type of mite, and a false positive reaction may occur to the other mite.

What about treatment?

Immunotherapy, either sublingual or subcutaneous, may be used if the owner doesn't want to feed a nondry diet.

Summary

Unfortunately, it takes only a tiny amount of mite allergen to elicit an allergic reaction in our pets. Hopefully, with more knowledge of these mites and ways to eradicate them, we can make our allergic pets more comfortable.

Dr. Alice Jeromin is a pharmacist and veterinary dermatologist in private practice in Cleveland, Ohio. She is a graduate of The Ohio State University College of Veterinary Medicine and an adjunct professor at Case Western Reserve University's College of Medicine in Cleveland.

References

1. Colloff MJ. Dust mites. Collingwood, Australia: CSIRO; 2009.

2. Brazis P, Serra M, Sellés A, et al. Evaluation of storage mite contamination of commercial dry dog food. Vet Dermatol 2008;19(4):209-214.

Suggested Reading

1. Reedy LM, Miller WH Jr, Willemse T. Aeroallergens and aerobiology. Allergic skin diseases of dogs and cats. 2nd ed. Philadelphia, Pa: WB Saunders l997;59-61.

2. Bensignor E, Carlotti DN. Sensitivity patterns to house dust mites and forage mites in atopic dogs: 150 cases. Vet Dermatol 2002 Feb;13(1):37-42.