Cat and dog allergens - can intervention studies solve their inscrutable riddle?

Allergy and asthma: Effects of the exposure to particulate matter and biological allergens

The prevalence of asthma and allergies including atopy has increased during the past decades, particularly in westernized countries. The rapid rise in the prevalence of such diseases cannot be explained by genetic factors alone. Rapid urbanization and industrialization throughout the world have increased air pollution and population exposures, so that most epidemiologic studies are focusing on possible links between air pollution and respiratory diseases. Furthermore, a growing body of evidence shows that chemical air pollution may interact with airborne allergens enhancing the risk of atopic sensitization and exacerbation of symptoms in sensitized subjects. These phenomena are supported by current in vitro and animal studies showing that the combined exposure to air pollutants and allergens may have a synergistic or additive effect on asthma and allergies, although there is an insufficient evidence about this link at the population level. Further research is needed in order to elucidate the mechanisms by which pollutants and biological allergens induce damage in exposed subjects. The abatement of the main risk factors for asthma and allergic diseases may achieve huge health benefits. Thus, it is important to raise awareness of respiratory allergies as serious chronic diseases which place a heavy burden on patients and on society as a whole.

Sensitization to rodents (mouse/rat) in urban atopic populations without occupational exposure living in Campania district (Southern Italy): a multicenter study

BACKGROUND

Up to now very few data on allergic sensitization to rodent allergens in Western Europe and Italy are available, and there are no information at district level.The aim of this report was to investigate clinical significance and characteristics of allergic sensitization to mouse/rat (M/Rt) allergens in atopic subjects living in Campania district (Southern Italy).

METHODS

Allergists from the whole Campania district were required to report the results of skin prick tests of at least 100 consecutive subjects. In 1,477 consecutive outpatients, we selected all subjects with an immediate skin reaction to M/Rt dander. Clinical history including a careful evaluation of the modality of exposure and the results of skin-prick tests (SPTs) were recorded.

RESULTS

Fifty seven patients were sensitized to M/Rt dander (5.78%). Two patients were mono-sensitized. Fourteen patients reported indoor conditions suggesting presence of rodents allergens at home. All patients exhibited low-moderate degree of SPT positivity to M/Rt. High frequency of concomitant allergic sensitization to dust mites was found.

CONCLUSIONS

Our results suggest that the role of allergic sensitization to rodents is not negligible in atopic subjects without occupational exposure living in Campania district area; these values are higher in comparison to those previously found in Naples area. Highly atopic individuals should be tested by SPTs/evaluation of serum specific IgE to rodents in the case they should begin an occupational exposure to M/Rt or keep these animals as pets.

The allergic sensitization in infants with atopic eczema from different countries

BACKGROUND

No study has compared allergic sensitization patterns in infants with atopic eczema from different countries. The aim of this study was to investigate the patterns of allergic sensitization in a cohort of infants with atopic eczema participating in a multicentre, international study.

METHODS

Two thousand one hundred and eighty-four infants (mean age 17.6 months) with atopic eczema from allergic families were screened in 94 centres in 12 countries to participate in a randomized trial for the early prevention of asthma. Clinical history, Severity Scoring of Atopic Dermatitis Index, measurements for total serum IgE and specific IgE antibodies to eight food and inhalant allergens were entered into a database before randomization to treatment. A history of type of feeding in the first weeks of life and exposure to animals was recorded.

RESULTS

A total of 52.9% of the infants had raised total IgE, and 55.5% were sensitized to at least one allergen. There was a wide difference in the total IgE values and in the sensitization rates to foods and aeroallergens among infants from different countries. The highest prevalence rates of allergen-sensitized infants were found in Australia (83%), the UK (79%) and Italy (76%). Infants from Belgium and Poland consistently had the lowest sensitization rates. In each country, a characteristic pattern of sensitization was found for aeroallergens (house dust mite > cat > grass pollen > Alternaria), but not for food allergens.

CONCLUSIONS

In infants with atopic eczema, there is a wide variation in the pattern of allergic sensitization between countries, and data from one country are not necessarily generalizable to other countries.

Rabbit allergens: a significant risk for allergic sensitization in subjects without occupational exposure

BACKGROUND

Although rabbits are becoming popular as pets, data about the characteristics of allergic sensitization to rabbit allergens in patients without professional exposure are scarce.

AIMS OF THE STUDY

To determine the characteristics of allergic sensitization to pet rabbits, and the role of direct and indirect exposure to rabbits and rabbit allergens in non-professionally exposed patients.

METHODS

From among 1124 consecutive outpatients, we selected all subjects with an immediate skin reaction to rabbit dander. A clinical history including a careful evaluation of the modality of rabbit exposure, the results of skin-prick tests (SPTs) and total/specific IgE antibodies were recorded. The prevalence of rabbit ownership in the Naples area was also calculated.

RESULTS

Among 753 SPT-positive patients, 20 (2.65%) were sensitized to rabbit dander (5 patients were mono-sensitized). Fifteen patients reported direct rabbit contact (7 were rabbit owners and 8 had occasional contact outside the home); 3 patients had indirect exposure through contact with rabbit owners and 2 patients denied any direct or indirect exposure. Rabbit mono-sensitized owners of pet rabbits had persistent (moderate-severe) symptoms. The prevalence of rabbit ownership is 1.56%.

CONCLUSIONS

In susceptible not professionally exposed individuals, direct rabbit contact and, in some cases, indirect or no apparent exposure, may induce allergic sensitization to rabbit allergens. A progressive increase in rabbit sensitization (also by indirect exposure) may be expected as a consequence of the increase in rabbit ownership.

Sensitization to rabbit allergens in Italy--a multicentre study in atopic subjects without occupational exposure

BACKGROUND

Rabbits as pets are becoming popular in Italy, but few data are available on sensitization to rabbits in patients without occupational exposure. In a multicentre study, we assessed the prevalence of rabbit sensitization in atopic subjects and their modality of exposure.

METHODS

Allergists from the whole country were required to assess the presence of skin prick test positivity to rabbits in about 100 consecutive patients with allergic rhinitis and/or asthma. In the rabbit-positive patients, clinical history, pet ownership and modality of exposure were assessed.

RESULTS

Skin tests were performed on 2,329 outpatients, of whom 1,602 had at least one positivity. Among them, 39 (2.43%) were sensitized to rabbit dander (4 monosensitized). The prevalence of sensitization ranged between 0.65 and 4.72%. Nineteen patients reported direct rabbit contact (10 for ownership and 9 for occasional contact) and 5 patients only indirect exposure through the contact with rabbit owners. Fifteen subjects denied any direct or indirect exposure. All the monosensitized patients were rabbit owners and had persistent (moderate-severe) respiratory symptoms.

CONCLUSIONS

Sensitization to rabbit in Italy is not to be neglected. In atopic subjects without occupational exposure, contact and indirect exposure to rabbits may induce sensitization. A progressive increase in rabbit sensitization is expected in the future as consequence of the increased rabbit ownership.

Human Hair: An Unexpected Source of Cat Allergen Exposure

BACKGROUND

Cat allergens are ubiquitous because the clothing of cat owners constitutes an important source of distribution of Fel d 1 in cat-free environments. Since Fel d 1 can adhere to a variety of surfaces, we sought to verify if human hair belonging to individuals with or without a cat at home might represent a reservoir and be a possible carrier of cat allergens.

METHODS

Seventy-three women (25 with a non-neutered male cat and 25 with a dog at home, and 23 controls without any direct contact with these animals) were recruited. The collection of material from hair was carried out using a modified version of a battery-powdered portable sampler. Particulate material was harvested onto glass fiber filters (25 mm in diameter, with a pore size of 2 microm; AP 20 Millipore, Milan Italy), extracted in phosphate buffer with BSA and then assayed for the evaluation of cat allergen using an ELISA based on anti-Fel d 1 monoclonal antibody.

RESULTS

Detectable levels of cat allergen were found in 2 controls, in 2 women with a dog at home and in 13 women with a cat at home, respectively.

CONCLUSIONS

In some women with a cat at home, hair constitutes a significant reservoir of Fel d 1. It is likely that these amounts of cat allergen might contribute to allergic sensitization when released in cat-free environments.

The effect of pet ownership on the risk of allergic sensitisation and bronchial asthma

An increasing volume of evidence suggests that early contact of children with the allergens of furred pets (especially those produced by cats) may determine a lower risk of developing allergic sensitisation to these materials. A possible explanation of this data is that an early inhalation of high levels of the major cat allergen Fel d 1 induces the production of IgG and IgG4 antibodies with a "protective" effect. Other authors have shown that the prevalence of allergic sensitisation to cats, in adults, is reduced in those patients exposed to the lowest and highest levels of the allergens. On the contrary, the risk of developing sensitisation to cats is significantly higher when the patients were exposed to intermediate levels of Fel d 1. Moreover, epidemiological studies have demonstrated a relatively low prevalence of cat allergy (about 10%) in some countries where rates of cat ownership are high. This data confirms the role of indirect exposure to pet allergens in inducing allergic sensitisation. Clothes of pet owners have been indicated as the carriers for the dispersal of these allergens in pet-free environments. However, it is important to point out that exposure of highly sensitised patients to relevant amounts of pet allergens (such as in a pet shows/shops) may determine a dramatic exacerbation of nasal and/or bronchial symptoms.

Cutaneous and serological responses to cat allergen in adults exposed or not to cats

BACKGROUND

The relationship between pet ownership and the risk of developing respiratory allergic sensitization to pet allergens is still controversial.

OBJECTIVE

To determine the degree of cutaneous immediate hypersensitivity and the levels of specific IgE and IgG4 antibodies to cat allergen in cat sensitized patients directly or indirectly exposed to this animal.

METHODS

We studied 112 adolescents and adults sensitized to cat allergens (43 with and 69 without a cat at home). There were also 52 control subjects, 27 atopic non-sensitized to cat and 25 non-atopic. The degree of immediate hypersensitivity was assessed by using, in duplicate, skin prick test with four five-fold dilutions of cat hair allergen extract with the content of its major allergen Fel d 1 quantified in micrograms plus positive (10 mg/ml histamine chlorhydrate) and negative (saline solution) controls. The resulting wheal areas were analysed by means of Parallel Line Assay. A blood sample was collected from every patient and control subjects for the evaluation of serological cat specific IgE and IgG4 antibodies.

RESULTS

Patients with cat at home had a lower cutaneous response than patients without this pet. The difference in the skin sensitivity was estimated in 3.4 times (P<0.01). There was no statistical difference between the levels of cat specific IgE antibodies in the two groups of patients (P=0.065). The levels of Fel d 1 specific IgG4 antibodies showed a statistically significant association with the presence of cat at home, with higher levels in patients owing cat at home than in patients without this pet (P<0.001).

CONCLUSION

The results of this study demonstrate that direct cat exposure in adolescents and adults with respiratory allergy is associated with a lower cutaneous response to cat allergenic extract, assessed by SPT and compared with indirect exposure. In patients with cat at home mean levels of specific IgE are statistically comparable whereas the levels of IgG4 are higher in comparison with subjects not exposed to cats. The role of indirect exposure to cat allergens in airways sensitization also in adults is emphasized. Moreover, patients with cat at home show a cutaneous and serological sensitization to cat allergen not higher in comparison with subjects not exposed to cats.