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.

Sensitization to horse allergens without apparent exposure to horse. Report of two cases.

It has been well established that occupational exposure to horses increases the risk of allergic sensitization to horse hair, on the contrary very few data have been published in individuals without direct contact with horses. We describe two cases of severe respiratory symptoms triggered by a single direct exposure in two patients with only 4-5 previous short contacts with horses during the entire their life, since they live in urban area of Naples. Cutaneous and serological diagnostic tests showed significant sensitization to horse dander other than some common inhalant allergens. Our report suggests that, in already (but unaware) horse-sensitized patients, the last direct contact with a horse has triggered severe respiratory symptoms. Passive carriage of horse allergen by the clothes of individuals in contact with horses/horse environments or a cross-reactivity between horse allergen (a lipocalin) and the major allergens (also lipocalins) of several furred animals are likely to explain our findings. Some other considerations can be derived by the clinical observation. First, it is likely that allergic sensitization to horse allergens could be more frequent than expected also in subjects without direct exposure to horse because of living in urban areas. Secondly, individuals suspected to be highly atopic or those already sensitized to some pet dander should be tested by SPTs/radio-allergo-sorbent test before the introduction of a pet indoors or, in the case of a big animal as the horse, a direct horse contact/entering into environments containing a horse.

Horse allergens: An underestimated risk for allergic sensitization in an urban atopic population without occupational exposure.

BACKGROUND: Data on allergic sensitization to horse allergen in modern urban areas are scarce. The aim of this study was to investigate the characteristics of allergic sensitization and the modality of exposure to horse allergens in atopic patients living in an urban area and without occupational exposure to horse and/or horse-derived materials. METHODS: From among 1822 consecutive outpatients, we selected all subjects who had an immediate skin reaction to horse dander. We recorded the patients' clinical history including a meticulous evaluation of the possibility and eventual modality of horse exposure, and the results of skin-prick tests (SPT) and total/specific IgE antibody analyses. RESULTS: Of 1201 SPT-positive patients, 35 (3.43%) were sensitized to horse dander. No patient was mono-sensitized. Six individuals reported having direct horse contact, 10 subjects had occasional contact with horse owners (indirect exposure), and 19 denied direct or indirect exposure to horses or horse allergens. Twenty of the 35 horse-sensitized patients reported both nasal and bronchial symptoms, 14 had rhinitis without asthma and one had asthma without rhinitis. CONCLUSIONS: Our results suggest that allergic sensitization to horse allergens is more frequent than expected in urban-dwelling subjects without direct or occupational exposure to horses. Highly atopic individuals or individuals who are sensitized to common pet dander should undergo SPT and evaluation of serum specific IgE before starting activities involving regular contact with horses such as riding, and before entering environments associated with horses.