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Q. We are looking into getting a family puppy, but we have a child who has been allergic to dogs in the past. Is it true that hypoallergenic dogs will not cause discomfort for an allergic child? We are currently looking into getting a Weimaraner puppy. Is there medication the child could take? Would slow exposure to the puppy build up a resistance?

A. Many patients hope to purchase a “hypoallergenic” dog or cat, but unfortunately these pets do not exist.

Avoidance is the most effective way to manage dog allergy.  Before bringing a pet into your home, I recommend you discuss your child's history with his or her allergist.

Although data suggest that children who are exposed to pets during infancy may be less likely to become allergic to dogs and cats in later life, in a child with history of an established dog allergy, slow exposure to the puppy would not be expected to desensitize your child.

Q. I have moved into a house where two cats lived. They are gone, but I am sick all the time with a cough and wheezing and headache, which I never had before. I am 80 years old with pulmonary hypertension, and I moved from an elevation of 6,000 feet to sea level. How long does the hair and dander remain after cats are gone?

A. Your first step should be to consult with an allergist to determine if you are asthmatic.  While asthma can develop at any age, if this is the first time you have had wheezing and coughing, your symptoms may not be related asthma.  Pulmonary hypertension can also cause respiratory symptoms, especially shortness of breath.

Your allergist can perform a simple in-office allergy test to determine if you are allergic to cats, dust mites, or other common allergens for your geographical region. 

In a home that previously had cats, it may take up to 20 to 30 weeks before the cat allergen concentration is reduced to the levels found in animal-free homes.  You may be able to speed reduction of the cat allergen by replacing carpet with hard surface flooring, removing any upholstered furniture and drapes used by the former owners, and cleaning the walls.  However, all homes, even those never occupied by a cat, will have a minimal level of cat dander that can be measured.

Your allergist should be able to provide medications to help reduce your upper and lower respiratory symptoms for as long as they are needed. 

Q. How long after being a dog-free house can I expect allergy symptoms to disappear?

A. The specific allergens from dogs are found in almost all homes with a dog, (as well as public buildings and schools) and approximately 15% of homes without a dog. Therefore, even after you find a new home for your pet, you might continue to have exposure to dog allergens, and symptoms related to these exposures.

Strategies to minimize symptoms include reducing or eliminating carpet within the home, using a high-efficiency vacuum with a double or micro-filter bag and using HEPA air cleaners. Although dog allergy symptoms may decrease with avoidance strategies in your home, exposure to dog allergen from sources outside your home may continue to cause bothersome symptoms. In this circumstance, medical treatment and/or allergen immunotherapy may be future options. You should discuss your symptoms and potential strategies for managing symptoms with your allergist.

Q. After a recent trip to the local animal shelter, my children want to adopt a dog or cat. I have a number of allergies and worry that my symptoms will become worse if we bring an animal into our home. I have heard that there are non-allergenic or hypoallergenic dogs, which allow an allergy sufferer to have a pet in their home without having symptoms. Is this true? If so, which types of dog would be considered non-allergenic. Are certain breeds of cats non-allergenic as well?

A. Unfortunately there are no "non-allergenic" cat or dog breeds! All of these have some level of allergen. The allergic potential of dogs or cats is not affected by the length of their fur. This is a common myth!

The protein that causes allergies is found in an animal's saliva, dander and urine. Almost 10 million pet owners – including children – are allergic to their animals.

The fur of a dog or cat can also collect additional allergens, such as pollen and mold spores.

Cats seem to be more allergenic than dogs. Almost all already-allergic people exposed to cats on a regular basis will develop a cat allergy. 

If you plan to introduce a pet into your home, have an evaluation by a board-certified allergist, including skin testing. This will tell you for certain what you are allergic to. If you are found to be allergic to dogs or cats, consider immunotherapy (allergy shots). These shots will eventually desensitize you to these animals, so that you may one day be able to have a family pet without compromising your health or well-being.

Q. I have been allergic to animal dander my whole life, but as some cruel twist of fate, I am absolutely crazy about animals. Fortunately, non-sedating antihistamines seem to relieve all of my symptoms. Despite my allergies, I'm considering getting a dog. Is there any harm in using an antihistamine every day? And will it continue to work with constant exposure to an allergen (in this case, dog)?

A. The use of long-term antihistamines is not a major concern in terms of drug safety. If you tolerate it now, you should continue to tolerate it. With the older, first generation antihistamines (e.g., diphenhydramine) there can be some loss of effectiveness (sub-sensitivity or tolerance), and while this may also apply to the newer, second generation, non-sedating antihistamines, the evidence is not conclusive.

However, when a patient lives with an animal, their exposure to the allergen is more intense. As a result, they may develop symptoms that are not adequately controlled with any oral antihistamine. In fact, most severely animal-allergic people often require more than one daily medication, and this usually includes a nasal steroid and an eye drop. While use of these medications on a daily basis is quite safe, we do not have data on safety for long-term (e.g., 20+ years) of daily use.

On the other hand, sometimes living with an animal actually slightly increases a patient's tolerance to the allergen, so that they have are fewer symptoms.

Unfortunately, there is not way to predict which of these scenarios will play out for you, or any other individual to a specific dog. You can be more allergic to one dog than another dog. In addition, a brief exposure to a specific dog may not predict how you will react to that same dog a few weeks later.

Another concern is that by allowing your nose to tolerate the dog (by taking an antihistamine), you are inhaling more dog dander. This increases the possibility of developing allergic asthma, as the lungs have a lining that is very similar to that of the upper airway. While this progression from nasal allergies to asthma is most common in children, it does also occur in adults.

If you are interested in having a dog, consult your allergist and consider starting on a course of allergen immunotherapy (allergy injections) to reduce your sensitivity to dog dander. This is the only form of preventative and long-term control medical treatment available. In addition, a dog-allergen-minimizing home environment would be helpful. Presuming you would have an inside dog, this might include hard surface flooring, leather furniture, a bedroom that is off-limits to the dog, and use of HEPA devices (vacuums and air cleaners).