Allergies to pets and other animals

Dr Harry Morrow Brown looks at a problem that can cause great upset within families

When we share a house with any pet there is always a risk that a member of the family will become allergic to it, especially if there is a family history of allergies. Demands from a child for a puppy or a kitten are difficult to refuse. Unfortunately by the time everyone has become fond of the pet a member of the family may have become sensitised, making it much more difficult to part with if necessary. Pets are best avoided in allergic families.

Contact with animals, their feed, their environment, and even their parasites is unavoidable for farmers, vets, jockeys and scientists whose careers depend on experimental animals. Occupational animal allergies can enforce a change of employment or career if severe and difficult to control with drugs.

What causes the allergy?
The protein that causes the vast majority of allergic reactions is found in the skin and saliva.

All animals shed hair and redundant scales of skin as dandruff. These flakes of skin are so light that they float in the air and settle at a rate depending on their weight. Some, especially cat dander and flakes of dried saliva from grooming, are so light that they never settle, explaining why cat allergic people will sneeze, wheeze, or get itchy eyes as soon as they enter a house where there is a cat, even if it is not to be seen or they do not know it is there.

Mice or rats as pets, pests, or used in laboratories cause allergies from airborne particles derived from dried male urine as well as from dander.

Animals can trigger not only rhinitis, conjunctivitis, asthma, and eczema but sensitivity to other environmental allergens.

If the symptoms of the allergy improve significantly every time the sufferer is away from home and reappear soon after they get back, a pet allergy should be suspected. GPs may not be aware of this scenario, which has become more prevalent since foreign travel became commonplace.

The diagnosis can also be confirmed by skin or blood testing but facilities are hard to find in this country. An improvised test, which anyone can use safely, is to cut off a tuft of pet hair and rub the hair gently into a small area of normal skin on the forearm. When positive, itching, redness, and a wheal will appear within 15 minutes. This test is very useful when unusual animals are involved, but is best carried out by your doctor in case the reaction is serious.

Cats probably cause more allergies than any other animal because they are to be found everywhere, and their dander and saliva particles float in the air indefinitely. Traces have been found everywhere, on cat owners’ clothes, in buses and trains, and in schools, so this allergen is almost impossible to avoid. The effects depend on how sensitive a person is.

For example a patient who knew he was very sensitive to cats bought a house after being assured that although the previous owners had a dog they did not have a cat. But once he moved in his asthma got much worse, so much so that he was admitted to hospital several times. It was only when he got to know the neighbours that he found out that their cat used to come into his house every night and cuddle up to the dog in front of the fire. He had to redecorate the house totally before his asthma could be controlled.

Another patient always had severe asthma if he spent the evening in the local pub, so he was advised to stop drinking beer as he was not affected by drinking vodka in other pubs. Some months later he returned to his local and drank a pint of beer with no ill effects. How come? The pub had meanwhile changed hands and the new owners had got rid of the cats, which had previously sat on the window watching him drink his beer.

For some years patients waiting to see me sat on a sofa covered with a very old tiger skin. I noticed that a young cat allergic, who had improved greatly since the cats had been found a good home, was obviously sneezy and wheezy by the time he came in to see me. Recalling that tigers were just very big cats I made an extract of the tiger hair and found that the boy’s skin test was just as big for tiger as for the domestic cat. Similar experiments showed that, for him, long haired cats were more allergenic that short haired ones.

‘Alternative’ cats
It is recognised that no traditional breed of cat is allergen free but for those who cannot bring themselves to live cat free there are a couple of breeds that appear to be easier to tolerate than others.

Surprisingly, one of these is the Siberian Forest cat - very handsome with a dense waterproof coat. His chest is barrel shaped and the contours of his face, which is a modified wedge, are soft with large, expressive eyes. Siberian cats are strong and muscular but have an agility which belies their appearance; their owners claim they have dog-like qualities of loyalty to their owners and seek interaction with them. They are believed to have earned their keep in Russia in the monasteries where they protected the granaries from rodents and kept watch in the high beams for strangers. In Soviet Russia cats were forbidden as pets and the Siberian did not develop a high profile until they arrived in East Germany in the 1980s. For UK breeders try Sapphirensteel Siberians in Nottinghamshire 01909 501 231/07986 708 071.

Not, maybe, as obviously attractive but apparently wonderful pets are Devon Rex cats, ‘the curly-haired pixie of the cat world’ whose fur also appears to cause relatively low allergic reactions. If you have access to the internet, the Rex Cat Association has a comprehensive list of UK breeders.

Dogs do not appear to contaminate the environment to the same extent, and I have shown that patients are more sensitive to some breeds than others. Nevertheless, dogs can cause serious asthma and eczema and are often overlooked as a possible cause. The possibility that dogs can cause eczema is seldom recognised in this country, so it is quite unknown how often this is true.

One remarkable case improved to some extent on a milk free diet, but then cleared completely on holiday in Spain. On the way home from Heathrow the family stopped to pick up the dog from the kennels, and by the time they got home the child was scratching himself to bits. After the dog was found a good home and the house was cleaned he became completely free from eczema as long as he avoided milk.

A 37-year-old nurse had had a dog for 18 years, and eczema for 14 years, which was better on holiday, but her dermatologist had no suggestions apart from steroid creams. Skin and blood tests for dog were strongly positive but she did not want to get rid of the dog. In this case the use of a tannic acid spray in the house and the dog’s bed was effective because this agent combines with and neutralises the dander.

Sandra was 12, and the referral letter stated that her asthma was mainly emotional because father was a criminal and often in jail. She sat there all hunched up, withdrawn, miserable, and certainly looked emotionally disturbed.

However, her peak flow rate was only 50, so she did not have the breath to do more than sit still. The asthma was brought partially under control with oral steroids but did not really resolve until the dog was put outside in a kennel.

Stephen was 13, and had such severe chronic asthma that he had a well developed pigeon chest deformity. He soon recovered in hospital on oral steroids but his mother could not accept that her beloved dog was the cause until he had a severe attack on returning home and was readmitted. He continued to relapse every time he returned home until the dog was removed.

When a beloved pet is identified as the cause of a child’s asthma or eczema the parents may find difficulty in accepting that the removal of the pet is the only sensible answer. This policy may not be pursued as vigorously as possible as many doctors have pets and are often unaware of the importance of allergy to pets. We are such a nation of pet lovers that expensive drugs may be used indefinitely to suppress the effects of the continued presence of a pet.

‘Alternative’ dogs
Although all dogs produce allergens via their skin saliva and urine, some people may only react to allergens from a specific breed. Dogs who shed their skin relatively infrequently (every 21 days) such as poodles, airedales and schnauzers, tend to produce fewer allergens than dogs who shed it every three to four days – such as cocker spaniels or alsatians.

Because it is the dander or skin scales that cause the most significant allergic reactions, short haired or hairless dogs, such as the Peruvian hairless Inca Orchid, will not help unless you are reacting to the allergens collecting in the dogs fur rather than the dander.

The website gives a good deal of information about low allergen breeds as does Dog Breed Info Center. Both give long lists of relatively low allergen dogs including the Bichon-Frise, a very popular small dog with soft curly hair, the Labradoodle (a cross between a labrador and a poodle), and the Malti-Poo (a cross between a Maltese and a poodle)...

Grooming horses produces a surprising amount of dander that may trigger asthma or rhinitis while the hay may contain pollen from the summer that can cause hay fever in winter. Mouldy hay can cause mould allergies and also farmers lung, a very serious disease which produces symptoms resembling influenza.

Horse riding can cause family problems. Big sister was very fond of her pony, but the traces of horse on her clothes caused life-threatening asthma in her little brother – a problem solved by changing her clothes before entering the house.

Antique furniture may be stuffed with horse hair, and cause sneezing and wheezing in anyone sitting or lying on it.

Other Animals
Any pet can cause an allergy problem, and testing solutions for an unusual pet may not be available. In this case a test can be carried out by rubbing some hair into the skin to cause a reaction, or by making a special extract for skin testing.

A good example is a lady who developed very severe sneezing attacks soon after her son was given a chinchilla as a birthday present. They vanished when she went on holiday. An extract of hair made in a syringe produced an impressive skin reaction. She was fortunate that she was soon to move to a new house, where the animal could be kept outside and she had no more trouble.

In another unusual case the skin scales from a hamster kept in a kitchen beneath a bedroom rose in the warm night air to trigger asthma in the occupant of the bedroom above.

The most exotic allergenic pet in my experience was a kinkajou or sugar bear. For many years nobody including the skin clinic suspected that it was the cause of this teenager’s chronic eczema, which was worst on the hands that touched the animal. When the animal died the eczema cleared up completely!

‘Alternative’ horses
One breed of horse with short, curly hair, which appears to cause relatively few allergic reactions is the Bashkir Curly, which is bred and mainly available in the USA. You will find a number of sites on the internet dealing with Curlies, including Oakesmuir Bashkir Curly Horses which exports to Europe.

Allergic reactions to horse dander can be reduced if the sufferer avoids grooming, which produces a great deal of dander. If the problem is cause mainly by the hay, sufferers may do better if the horse eats hay that has already pollinated. The horse’s bedding is also a potential source of trouble, but this can be dealt with by substituting synthetic material, which is now available. This can also be helpful to the horse if it too suffers from allergies – which a surprising number do.

For further information consult Dr Morrow Brown’s website


First published in 2008; revised 2013


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