'Dog Dust' May Combat Allergies and Asthma

Exposure to "dog dust," or the dried flakes of skin that fall from Fido, may protect against developing allergies and asthma in later life by altering intestinal bacteria, a new study in mice suggests. The dust appears to contain bacteria that, when present in an animal's gut, affects the production of immune cells in the animal's airway.

"Perhaps early life dog exposure introduces microbes into the home that somehow influence the gut microbiome, and change the immune response in the airways," said study researcher Susan Lynch, an associate professor of medicine at the University of California, San Francisco.

Past research has shown that exposure to pets, particularly dogs, during infancy may prevent people from developing allergies, and other work has found that bacteria in the gut can affect allergies and asthma. The new study adds to the research because it links these ideas — showing that the reason exposure to dog dust may prevent allergies is that the dust affects the population of gut microbes.

In the study, Lynch and her colleagues exposed mice to dust from a dog owner's home, and then tested the mice's immune response to cockroach allergens and ovalbumin (a component of egg whites), two substances that commonly trigger asthma attacks. They found that mice exposed to dog dust had fewer immune cells in the airway that respond to allergens, compared with mice not exposed to dog dust.

The findings hint at a mechanism for how dog exposure may protect against allergies or asthma. "It seems to be that early life exposure to dogs, and cats to a lesser extent, can protect against asthma allergens," Lynch told LiveScience, though she stopped short of recommending exposing infants to dogs. Lynch added that the findings fit in well with the hygiene hypothesis, the theory that a lack of exposure to beneficial microbes is linked to the development of autoimmune diseases and asthma in western nations.

The researchers also found the gut microbial makeup of the two rodent groups differed: The mice exposed to dogs had more of the bacteria Lactobacillus johnsonii, an organism found in the dust from dog-owner homes. When the researchers added L. johnsonii to the diet of the unexposed mice, they found the mice showed a reduced immune response in their airways to both, though not as much as mice originally exposed to the dog dust.

The next step will be understanding exactly what these microbes are doing in the gut, and how they affect the immune response in the airway, Lynch said.

Ultimately, understanding this process could lead to the development of microbial-based therapies to treat or prevent asthma.

Hypoallergenic Dogs Not Allergy-Proof

Although they've long been considered an allergy sufferer's best friend, so-called hypoallergenic dogs do not have lower household allergen levels than other dogs, according to a new study that measured allergen levels in babies' nurseries.

Dog breeds classified as "hypoallergenic" are believed to produce less dander and saliva and shed less fur. Researchers at the Henry Ford Hospital (HFH) in Detroit put this theory to the test by measuring environmental allergen levels in the houses of 173 dog owners one month after a newborn baby was brought home.

Researchers collected dust samples from the carpet or floor of each baby's bedroom and measured the levels of the dog allergen Can f 1. Only homes with one dog per family were involved in the study, and 60 dog breeds were analyzed overall, 11 of which are considered hypoallergenic dogs.

"We found no scientific basis to the claim hypoallergenic dogs have less allergen," said Christine Cole Johnson, chair of HFH's Department of Public Health Sciences and senior author of the study.

Dogs are often classified as hypoallergenic using one of four "schemes" based on their breed in order to compare allergen levels. Scheme A compares purebred hypoallergenic dogs to purebred non-hypoallergenic dogs, while scheme B compares purebred and mixed breed dogs with at least one hypoallergenic parent to purebred non-hypoallergenic dogs.

Scheme C compares purebred and mixed breed dogs with at least one hypoallergenic parent to purebred and mixed breed dogs with no known hypoallergenic component, and scheme D compares only purebred dogs identified as hypoallergenic by the American Kennel Club to all other dogs.

The study showed that all four schemes yielded no significant differences in allergen levels between hypoallergenic dogs and non-hypoallergenic dogs. In fact, in homes where the dog was not allowed in the baby's bedroom, the allergen level for hypoallergenic dogs was slightly higher compared to allergen levels of non-hypoallergenic dogs.

"Based on previous allergy studies conducted here at Henry Ford, exposure to a dog early in life provides protection against dog allergy development," Cole Johnson added. "But the idea that you can buy a certain breed of dog and think it will cause less allergy problems for a person already dog-allergic is not borne out by our study."

Scientists Closer to Cat Allergy Cure

Scientists say they're hopeful that a research breakthrough will lead to a cure for people who are allergic to cats.

Researchers at the University of Cambridge say they've figured out how a particular protein in cat dander triggers an allergic response in humans. Many people are allergic to cats, dogs, and other animals. Typical symptoms include sneezing, itchiness, and a stuffed or runny nose. Allergic reactions happen when the immune system overreacts to a perceived danger. Normally, the immune system identifies and responds to harmful viruses and bacteria. But with an allergy, the immune system wrongly identifies an allergen as dangerous, such as pet dander, and starts an immune response.

The most common cause of severe allergic reactions to cats is a protein called Fel d 1, which is found in microscopic pieces of animal skin (often accompanied by dried saliva) from grooming.

The Cambridge team discovered how this protein can trigger an inflammatory response when in the presence of a common bacterial toxin found in the environment called lipopolysaccharide, or LPS.

"How cat dander causes such a severe allergic reaction in some people has long been a mystery," said Clare Bryant, who led the research at the University of Cambridge’s Department of Veterinary Medicine. "Not only did we find out that LPS [intensifies] the immune response’s reaction to cat dander, we identified the part of immune system that recognizes it, the receptor TLR4."

The scientists then used medication that curbs the TLR4 response and found it blocks the effects of the cat dander protein on human cells, thereby preventing an inflammatory response.

Bryant says she's hopeful that the research will lead to new treatments for people with cat allergies, and possibly those with dog allergies.

What about allergies to pets?

The "dander," or skin shedding, of an animal is more potent in causing allergic reactions than the animal's fur or hair. In addition to the skin sheddings and fur, allergic reactions can occur to the saliva and/or urine of cats, dogs, horses, and rodents.

The scope of the animal allergy problem is enormous. These allergies are believed to affect up to 20% of North Americans and are directly related to the increasing popularity of pets, particularly cats and dogs. Studies have shown that dog allergens were found in all examined homes in the U.S., even those without family dogs. Likewise, almost all homes were shown to contain cat allergens.

Cats

The most well-known indoor allergy is probably due to Felis domesticus, the domesticated cat. The main allergen is a protein that is produced by the sweat glands (sebaceous glands) in the skin and appears in the skin flakes or dander that are shed from cats. The allergen is also found to a lesser degree in the fur, saliva, and urine of cats. Even with a past history of tolerance to cats, it is possible for a person with an allergic tendency to develop a sensitivity to cats after constant exposure.

The cat dander allergen is not only confined to the cat but also clings stubbornly to carpets, walls, and furniture. The protein can linger there for months and can serve as a reservoir from which allergens can become airborne when disturbed. The allergen is also lightweight and can float in the air for hours. People can also carry the cat allergen around on clothes, thereby spreading it to work, school, or a friend's house. Accordingly, for those who are allergic to cats, it does not reduce the risk of allergic reaction to simply isolate the cat in another room of the house. The cat dander is present wherever the cat generally exists, and it is this dander that is the problem.

Allergy facts

An estimated 30% of households in North America have at least one cat.

About 6% of the population is allergic to cats.

Dogs

Domesticated dogs (Canis familiaris) are found in over 40% of homes in North America. About 33% of allergic individuals are sensitive to dog dander (as compared with almost 50% of allergic individuals who are cat-allergic). Since the allergic reaction is prompted by skin shedding and not fur, it makes little difference whether the dog has long or short hair; you can be as allergic to a Chihuahua as you can to a sheepdog. Small dogs can also cause as many allergy symptoms as large dogs. There is certainly no evidence that one species is less allergy-provoking than another one. Clearly, no breed is non-allergenic. Even poodles and wheaten terriers (often thought to be hypoallergenic) will likely induce allergy symptoms in sensitive individuals upon continuous exposure.

If your child has asthma and a known allergy, be especially careful not to allow the child to spend the night at the home of a friend or relative with a pet. Severe allergic reactions and even fatalities have been reported. Do not let this happen to your family or your friends.

Horses

Only 10% of allergic individuals have a sensitivity to horses. The reason is probably due to less exposure since there is little horsehair in furniture or bedding anymore. Sensitive people, however, must avoid not only horses and stables, but also objects directly related to them, such as bridles, saddles, and riding clothes. Also be aware that horsehair may still be found in antique furniture and old toys. People who have problems with horses may also react to donkeys, mules, and zebras.

Allergy alert

Remember that a trip to the barn not only exposes you to animal dander, but also to mold, pollen, and lots of other irritants as well. If you suffer from asthma, be careful and be prepared.

Birds

Allergy to birds is more common among bird breeders where the exposure is highest. People who are sensitive to the feathers of chickens, geese, turkeys, and ducks can still eat the meat or eggs from these animals. They may well react, however, to the feathers in down comforters, pillows, and duvets. You should also remember that dust mites, another common allergen, hide in these bedding accessories.

Rodents

This family includes hamsters, rabbits, guinea pigs, gerbils, ferrets, mice, and rats. Most allergic reactions are caused by exposures in laboratories, but these animals are also common pets. Mouse urine is an especially potent allergen for personnel that handle laboratory animals. The urine of rats and guinea pigs also contains allergens as do the saliva and fur of rabbits. Rabbit hair can be found in fur coats, glove linings, slippers, foot muffs, pillows, and quilts. The fur of the Angora rabbit is said to be 10 times warmer than that of sheep wool. The soft yarn spun from Angora rabbit fur can be found in hand-knitted trimming, crochet work, gloves, hosiery, and knee pads. Alone or mixed with silk, it is also used in sportswear. And, of course, rabbits often appear in schools as the classroom pet.

Allergy alert

Frequently, parents will report that their child has "won the privilege" of caring for the classroom pet over the weekend or the holiday vacation. This often leads to the onset of a particular animal sensitivity. If you or your child already has allergies or asthma, do not volunteer for the job.

Allergies to animals

This type of allergy distributed very widely and it can significantly degrade over its other manifestations. Pets are one of the strongest sources of allergens. Unlike what is commonly spoken, let us say that animals do not produce allergens - just wool is their excellent container.

Examples of animal allergens:

* Saliva (dogs, cats, horses, etc.)
* Urine (cats, dogs, small laboratory animals)
* Serum (of blood)
* Horny flakes (desquamated skin)
* Epithelium (desquamated skin)
* Excrement (parrots, pigeons and others)

The impact on the patient's allergy occurs when inhaled dust. Most frequent allergic to cats, but the most severe forms marked with allergies to horses and small rodents.

Everyone knows that cats are spending too much time on workaround. In doing so, they leave a large number of allergic saliva in your hair, saliva and then spread everywhere. Furthermore, when workaround cats scatters in the ambient air entire cloud of tiny drops saliva - they are literally "dispensers allergies!

In patients with allergic to dogs, she noted on any of their breed. Short-haired dogs with the same allergens as long-haired. Allergy birds are often indirect nature: develop sensitization not to peryam, and by parasitic mites in their mass.