Cat | Dog
Allergens from cat epithelium and dander are one of the most common causes of respiratory allergic disease. Several cat allergens have been identified and characterised.
Carpets, mattresses and upholstered chairs are reservoirs of cat allergens. Cat allergens are carried on human clothing into environments never visited by cats. Transport of cat allergens on clothing from the domestic to the school environment is in fact a major source of cat allergens in classrooms.
Cat-allergic patients have been shown also to react to “big cats” e.g. ocelot, tiger and lion. A subgroup of cat-allergic patients also reacts to dogs and sometimes to other animals. Serum albumin is the main common component. Extensive cross-reactivity even occurs between albumins of distantly related species such as horse, cattle, pig, rodents and furred animals. However, great variability exists between patients and selective sensitivity to limited numbers of species occurs.
Allergy to cat dander and pork meat, also referred to as the pork/cat syndrome, was shown to be mediated by IgE antibodies recognising cat and pig serum albumin. In addition, other kinds of meat may be a risk for patients with this type of sensitivity.
IgE-mediated sensitisation to cat is a risk factor for asthma. Allergen exposure plays a causal role in the development of bronchial hyperreactivity and of the chronic inflammatory responses seen in patients with asthma. Infants exposed to cats developed skin prick test sensitivity about three times more often than those without such exposure.
Furthermore, the low level cat exposure that occurs in many homes without cats can induce symptoms in some patients who are sensitive to cats.
Tobacco smoke, prenatal and postnatal, has been shown to have an adjuvant effect on cat sensitisation in exposed children. Allergic reactivity to pollens may also be aggravated by environmental priming with ubiquitous animal dander. Furthermore, allergy to cats or dogs seems to be an important risk factor for the development of laboratory animal allergy. Avoidance of cat allergens is an important measure to take in the treatment of sensitised asthmatics, decreasing symptoms and decreasing the need for drugs.
Only removal of the cat leads to a lasting decrease of the allergen exposure.
The dog, a relative of the wolf, the jackal and the fox, was one of the earliest domestic animals, living in human communities as early as 12,000 years ago. More than 800 breeds have been developed.
Dog allergens have been found in serum, dander, pelt, hair and saliva.
Although allergen differences occur according to the origin of the allergen (e.g. dander or saliva), no breed specific allergens occur. But the concentration of allergens varies within breeds and among them.
Dog dander contains the highest proportion of dog-specific allergens. Animal dander is extremely lightweight and tiny in size and can stay airborne for hours.
Levels of dog allergens in houses with dogs may reach high levels. Levels in homes without dogs are generally 10 to 100 times lower, but can still be detected.
In houses with dog allergens, the highest concentration appears to occur on the living-room floor, on furniture and in bedrooms.
Dog allergens can be detected also in other places, such as schools and day-care centres where dogs are not present on a regular basis. The allergens appear to be transported on clothes and may be present in relatively high concentrations.
An extensive cross-reactivity among the different breeds could be expected.
It has been noted that many patients allergic to cats are also allergic to dogs. Many studies suggest evidence for cross-reactivity between some cat and dog allergens.
Dog dander is an important source of inhalant allergens and may frequently induce symptoms in sensitised individuals. Symptoms include asthma, allergic rhinitis and allergic conjunctivitis. 30–35% of atopic individuals display allergic symptoms on exposure to dog allergens.
Symptoms can be caused by indirect exposure to dog dander in schools, at work and on public transport. In sensitised subjects, repeated exposure to allergens also contributes to subclinical inflammation, hyper responsiveness and general worsening of asthma.
Eczema following exposure to dog allergens has been reported.
Occupational allergy to dog may also occur in animal workers, animal pelt workers and laboratory workers.