In scientific terms, it is difficult to determine the number of people with animal hair allergies. One of the reasons is because blood and skin tests only show whether the body has developed an allergic predisposition to a certain allergen. At this time, these tests cannot confirm or predict whether a patient will actually develop symptoms.
In order to estimate the prevalence with any certainty, elaborate studies would be required in which the study participants would be directly exposed to the allergen. Even though there are no current findings as to how many people experience symptoms due to contact with animal hair, there is a series of studies investigating how many people have a predisposition to developing an allergy. A study conducted on 3,000 patients across Europe revealed that this predisposition, or sensitisation, varies widely depending on the region. Scandinavian countries have the most people with animal hair sensitisation (56% in Denmark compared to only 16% in Austria). One recent study of a random sample of 7,000 people in Germany revealed that around 10% of the population is sensitised to animal hair.
The first animal hair allergen, Fel d 1, was identified in 1991. This is the main allergen in cats (felis domesticus) and is produced in the animal’s sebaceous, salivary and anal glands. Whenever the cat cleans itself, the allergen is spread onto its fur. All cat species – long-haired and short-haired, from tigers to lions – produce this allergen.
Most ‘animal hair allergens’ are not part of the animal’s hair in the strict sense. It is often the small skin particles or substances found in bodily fluids (urine, saliva, sperm) that trigger allergies in humans. The trigger substances are needed for the animals to function; some are required for their sense of smell, others for the immune system and social behaviour.
Since each animal is a carrier of different allergens and each individual has a different sensitisation pattern, there are no truly ‘allergy friendly’ pet species. The vast majority of people who are allergic to cats react to all cat species. On the other hand, people who are allergic to dogs may be able to tolerate individual dog species or just female dogs, depending on the sensitisation of the patient. However, this can only be revealed through a comprehensive diagnostic procedure.
Some animal hair allergens are similar to proteins from other animals. This is why, in very rare cases, allergy symptoms can develop in people who are sensitive to a specific cat allergen (Fel d 2) after eating pork. Referred to as ’pork-cat syndrome’, this occurs when substances in pork are considered dangerous by the immune system of an individual with a cat hair allergy. Since this substance is heat sensitive, pork-cat syndrome usually only occurs after raw or partially cooked pork is consumed.
Although cats and dogs are the most common allergy triggers, horses, cows, rabbits, hamsters, guinea pigs, rats and mice can also provoke allergy symptoms. Animal hair allergies affect livestock holders, people without pets, and people who work closely with animals, such as veterinarians, zookeepers and farmers.
Animal hair allergies principally affect the breathing and the skin, with symptoms such as itching, redness, conjunctivitis or hives. They can also trigger or worsen an atopic dermatitis flare-up. If the allergens are breathed in, they can trigger allergic rhinitis or asthma symptoms in sensitised people.
Like other allergies, animal hair allergies are diagnosed in several phases. As a first step, the doctor asks the patient about his or her living conditions and symptoms and tries to identify the possible causes. If an allergy is suspected, a skin or blood test is conducted, depending on the symptoms, in order to confirm it. These tests reveal an allergic disposition to a certain substance but do not provide evidence of an actual allergy. This is why an additional diagnostic procedure, the provocation test, is conducted to rule out any doubts. For this test, the patient receives a minute amount of the allergen – for example, on the nasal mucosa. The results confirm whether a specific animal triggers an allergic reaction or whether it can be removed from the list of suspected allergens.
A pet owner may be faced with a tough decision. But an important step in the treatment of allergies is to create an allergen-free environment, which will help prevent allergy symptoms from worsening over the long term and also keep the allergy from spreading to the lower respiratory tract. This sometimes means having to part with a beloved pet.
For exceptional cases in which contact with animals cannot be avoided – if the patient is a veterinarian, for example – specific immunotherapy (SIT) is an option. Data on the effectiveness of this therapy are available mainly for cat hair allergies. However, serious side effects have been observed more frequently in SIT for animal hair allergies than for other allergy triggers. Allergen avoidance is therefore still the most effective and recommended way to reduce symptoms. Medications are also available to treat symptoms.
Prof. Dr. med. Dr. h.c. T. Zuberbier
Last changes made: July 2016