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.

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.

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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.

— Update: 08-02-2023 — cohaitungchi.com found an additional article Could storage mites in pet food lead to false-positive food allergy diagnoses? from the website www.dvm360.com for the keyword how to avoid storage mites in dog food.

Canine atopic dermatitis is an inflammatory skin condition associated with the production of immunoglobulin E (IgE) specific for a substance that is either ingested or inhaled. Typical signs include pruritus, erythema, lichenification, seborrhea, and lesions from chronic inflammation, licking, chewing, and scratching. House dust mites (HDM) of the Dermatophagoides genus are the most common allergens recognized by the circulating IgE of atopic dogs. In laboratory experiments, dogs that are sensitized to HDM experience atopic flares when exposed to various species of storage mites. Because storage mites commonly grow on cereals used in commercial pet foods, researchers conducted a literature review to determine whether allergen cross-reactivity could lead to a false-positive diagnosis of food allergy. The results of their study were published in BMC Veterinary Research.¹

The investigators searched two databases for detailed studies using a series of key words. Of 87 identified articles, 10 were selected that were common to both database searches. Five articles reported results from laboratory studies, and five reported on field studies.

Laboratory studies

The survival and multiplication of Dermatophagoides HDM was first reported on dry dog food in 1972.² Nearly 40 years later, Tyrophagus putrescentiae storage mites were shown to survive and grow on three commercial dry dog foods.³ Tyrophagus mites grew on all three dog foods, with the highest numbers of mites found whenever molds had been allowed to grow on the kibble.

In 2015, samples of dog foods stored in nine different sealed plastic bags and in a lidded cup were evaluated to see whether T. putrescentiae could infest and proliferate them.⁴ After 3 months, Tyrophagus storage mites were discovered in 55% of the bags. Mites had not made holes in the packaging itself but had entered the bags via faulty seals. Lidded cups were not contaminated. The same year, investigators evaluated whether T. putrescentiae storage mites preferred to grow on protein-, fat- or carbohydrate-rich diets and found they grew best on the dog foods richer in proteins and fat.⁵ 

Finally, in 2016, several experiments were conducted to evaluate the growth of T. putrescentiae in different conditions.⁶ In the first experiment, mites were found to grow better on green and brown rather than white and red colored kibbles. (Whether the different-colored kibbles had different nutrients was not explained.) The second study found higher mite growth when kibbles were crushed rather than intact, and when the initial mite population density was highest. The third showed that four different strains of Tyrophagus mites grew better on crushed dog food than a commercial mite diet. The final experiment confirmed that a high initial mite inoculum leads to a higher final mite count.

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Field studies

In the first field study, 30 purchased and 50 pet owner–obtained commercial dry dog food samples tested with an enzyme-linked immunosorbent assay for HDM were all negative.⁷ In another study, 23 bags of commercial dry dog foods were tested for mite contamination by microscopy.⁸ Even though the bags were opened and closed twice daily over a 6-week period during this study, storage mites were not discovered.

The influence of different storage conditions on the contamination of dry dog foods with storage mites was first reported in 2008.⁹ Dry dog food bags were kept for 6 weeks in either laboratory storage with low average temperature and humidity or a ventilated garage with high temperature and humidity. More mites were detected in the bags stored in high temperature and humidity conditions.

In 2011, identical bags of a single commercial dry dog food were stored in 10 different households.¹⁰ Each bad was divided equally between the original sack with its reusable seal, a paper bag whose top was rolled for closure, and a plastic box with a sealed lid. These containers were stored next to each other, and the food was sampled every month for storage mite detection. After 3 months, mite numbers were significantly higher in the food samples stored in paper bags (60% of bags had evidence of mites) compared with baseline.

In the last field study, dog owners in eastern Australia provided 20 samples of commercial dry dog foods stored in open bags or storage boxes in home environments.¹¹ The food samples were examined for the presence of storage mites, and a small portion was kept for 2 additional months before their incubation under higher humidity and temperature conditions. Finally, nine new bags of commercial dog foods were purchased and tested as above. Mites were undetectable in any specimens after any of the incubation times. Similarly, storage mites were not observed when opening newly purchased bags or after storing the foods for 6 weeks at room temperature. In contrast, when incubating samples of these foods at high temperature (26 °C [78.8 °F]) and humidity levels (80%), storage mites were present as early as 3 weeks after beginning the experiment and in 78% of foods after 6 weeks of incubation.

Conclusions and take-home

— Update: 09-02-2023 — cohaitungchi.com found an additional article Food Mite Allergy: What Food is Mite-Free and How to Store It? from the website powerofthepaw.org for the keyword how to avoid storage mites in dog food.

Food mites in the food

Many cats and dogs are allergic to food mites. Read here how you can prevent contamination of the food by simple tricks and make life easier for your pet with a food mite allergy.

What are food mites?

Food mites (storage mites) are tiny arachnids very similar to house dust mites. They are not visible to the naked eye, however, you can tell when food mites have proliferated in it.

Food mites are very resistant and widespread in our environment, for example in house dust. The mites are usually killed by heating them above 60°C (e.g. in the washing machine) or by freezing them for several days.

What is a food mite allergy?

Allergies to food mites are almost as common as to dust mites and many animals are allergic to both types of mites at the same time. The immune system has an exaggerated reaction to both the mites themselves and the mite feces. Typically, affected dogs and cats show e.g. itching and inflamed skin (atopic dermatitis). It is then often suspected that it is an allergy to food components in the feed (e.g. egg or beef). A feed allergy can be combined with a feed mite allergy, but it does not have to be.

How do the food mites get into the feed?

Basically, there are three ways that storage mites can get into pet food:

1. The raw materials can already be contaminated with mites, e.g. grain.
2. During processing and filling of the feed, mites from the environment can get into the feed packaging if the plant is contaminated with dust or flour residues, for example.
3. During storage at home, storage mites from house dust colonize the feed. The risk of contamination increases the longer dried feed is stored. If the food is not in an airtight package, but in an open food bag, for example, colonization with food mites is all the faster.

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How often is dog and cat food contaminated with storage mites?

Various scientific studies have shown that freshly purchased store-bought pet food is usually not contaminated with mites. However, expired closed feed and feed that has been stored open for a longer period of time have definitely been found to be colonized with food mites more frequently.

What do the feed manufacturers do to keep their feed free of mites?

In the case of “normal” dog food or cat food, it is not usually necessary to take special precautions against feed mites during production. The usual hygiene standards are sufficient to prevent heavy contamination, and the usual heating during processing reliably kills any mites that may be present in raw materials.

However, absolute freedom from mites is important for dietetic food, especially for food for allergy sufferers. For this reason, manufacturers such as Royal Canin, for example, apply particularly high quality standards in the purchase of raw materials and in production, and regularly test their feeds to ensure that they are mite-free.

How can I tell if the feed is contaminated with mites?

If food mites have multiplied in the feed bag or feed garbage can, the dry food will take on a “minty” odor. You will find brownish looking mite dust at the bottom of the empty container.

How can I prevent food mites from contaminating our dry food?

If your dog has a food mite allergy, you should feed a diet food for allergy sufferers to be absolutely sure you are feeding a mite-free, uncontaminated food. Canned food for allergy sufferers is and will remain mite-free, but with dry food, a lot depends on how you store it.

The most important precautions to take when storing feed are:

• Use an airtight container to store the feed.
• Open the feed container only briefly to remove the daily ration and use a clean (washed) feed cup, feed spoon or similar.
• Wash out the empty feed container regularly with hot water.
• Storage mites can also be found on food for human consumption, e.g. on the outside of flour packaging. Therefore, store pet food separately from other food.
• Storage mites also live in house dust. True mite breeding grounds are e.g. mattresses, upholstery, pet beds, etc.. Therefore, please do not store dry food next to the dog bed or similar.
• Food mites can be found in large quantities in hay and straw. Therefore, storing dog or cat food in the barn is also not recommended. Allergic dogs and cats may experience problems after a barn visit.

The shorter you store the dry food at your home, the lower the risk of mite contamination. You can either:

Buy small bags of feed more frequently, rather than a large one every few months, or

• Freeze some of the dry food, since storage mites do not survive in the freezer (i.e., cannot migrate or continue to reproduce).

How useful is freezing dry food for food mites?

If you freeze a mite-free dry food (allergy food), it will remain mite-free as a result. However, if the food was already contaminated with mites or mite feces prior to freezing, the food mites may not continue to multiply, but your dog or cat may still have an allergic reaction even with minor contamination of dead mites or mite feces. In addition, mite-free dry food may become contaminated with mites on the food cup or bowl after thawing.

What else can I do to make life easier for my pet with a food mite allergy?

Food mites are found in house dust and dogs or cats with a food mite allergy are often allergic to dust mites as well. Therefore, food mite allergy sufferers should have as little contact with house dust as possible.

You can ensure this by, for example.

1. Washing dog blankets, cat beds or similar weekly at 60°C.
2. Do not let your pet sleep in the bedroom, as a lot of mites live in mattresses and bedding.
3. Treat the environment (not the food, of course) with a mite spray.
4. Quarantine your pet while vacuuming and/or equip the vacuum cleaner with an allergen filter.
5. When furnishing the home, make sure the floors and furniture are wipeable, if possible.
6. Keep the humidity in the house below 50% if possible.