- Open Access
Allergic sensitization to common pets (cats/dogs) according to different possible modalities of exposure: an Italian Multicenter Study
- G. Liccardi1, 2Email author,
- L. Calzetta2, 3,
- G. Baldi4,
- A. Berra5,
- L. Billeri6,
- M. Caminati7,
- P. Capano8,
- E. Carpentieri9,
- A. Ciccarelli10,
- M. A. Crivellaro11,
- M. Cutajar12,
- M. D’Amato13,
- I. Folletti14,
- F. Gani15,
- D. Gargano16,
- D. Giannattasio17,
- M. Giovannini18,
- C. Lombardi19,
- M. Lo Schiavo20,
- F. Madonna21,
- M. Maniscalco22,
- A. Meriggi23,
- C. Micucci24,
- M. Milanese25,
- C. Montera20,
- G. Paolocci14,
- R. Parente26,
- A. Pedicini27,
- R. Pio20,
- F. Puggioni28,
- M. Russo1,
- A. Salzillo1,
- P. Scavalli29,
- N. Scichilone30,
- B. Sposato31,
- A. Stanziola13,
- G. Steinhilber32,
- A. Vatrella33,
- P. Rogliani2, 3,
- G. Passalacqua34 and
- On behalf of Italian Allergic Respiratory Diseases Task Force
© The Author(s) 2018
- Received: 4 December 2017
- Accepted: 22 January 2018
- Published: 2 February 2018
The query “are there animals at home?” is usually administered for collecting information on anamnesis. This modality to consider exposure to pet allergens constitutes a potential bias in epidemiological studies and in clinical practice. The aim of our study was to evaluate/quantify different modalities of exposure to cat/dog in inducing allergic sensitization.
Thirty Italian Allergy units participated in this study. Each centre was required to collect the data of at least 20 consecutive outpatients sensitized to cat/dog allergens. A standardized form reported all demographic data and a particular attention was paid in relieving possible modalities of exposure to cat/dog.
A total 723 patients sensitized to cat/dog were recorded, 359 (49.65%) reported direct pet contact, 213 patients (29.46%) were pet owners, and 146 subjects (20.19%) were exposed to pets in other settings. Other patients were sensitized by previous pet ownership (150–20.75%) or indirect contact (103–14.25%), in 111 subjects (15.35%) any contact was reported.
Only 213 patients (29.46%) would be classified as “exposed to animals” and 510 (70.54%) as “not exposed” according to usual query. Our classification has shown that many “not-exposed” subjects (399–55.19%) were “really exposed”. The magnitude of exposure to pet allergens at home is not related exclusively to pet ownership. These considerations should be taken into account during the planning of epidemiological studies and in clinical practice for the management of pet allergic individuals.
- Allergic rhinitis
- Allergic sensitization
- Bronchial asthma
- Pets exposure
Exposure to animal allergens constitutes a relevant risk factor for the development of allergic sensitization and respiratory allergic diseases, such as asthma and rhino-conjunctivitis in susceptible individuals . In all developed countries cats and dogs are the most common pets living in indoor environments and the frequency of their ownership is highly variable, according to cultural differences and environmental factors [2, 3]. Cat and dog allergens should be considered ubiquitous because they are found not only in indoor environments, where these animals are kept, but also in other indoor private or public places where cats/dogs have been never kept . Although the presence of a pet at home is considered usually the main risk factor for allergic sensitization, dynamic distribution of the main pet allergens indoors is complex and depends by production, aero-dispersion, sedimentation and passive transport through clothes and other items [5–9]. These variables determine a diffuse presence of pet allergens (indirect exposure) also in indoor environments without pets and in environments where pets are no longer present for a long time (e.g. voluntary removal or re-location, natural death etc.) [10–12]. The query “are there animals at home?” is common and usually administered by researchers, physicians and pulmonologists/allergologists to patients for collecting information on anamnesis . This prevalent modality to consider exposure to pet allergens constitutes a potential bias in large epidemiological studies on the relationship between pet-exposure and allergic sensitization . We believe that an accurate medical history on pet exposure is essential also in clinical practice for an objective evaluation of the risk and the clinical significance of the skin-prick-test (SPT) positivity to pet (cat/dog) allergens, as well as for the management of sensitized patients (pet-avoidance measures, allergen immunotherapy, pharmacological treatment of respiratory symptoms etc.) . The aim of our study was to evaluate and quantify the role of different modalities of exposure to cat/dog in inducing allergic sensitization in a consistent population of cat and/or dog sensitized individuals living in Italy.
Characteristics of the patients sensitized to dog/cat allergens (total no. = 723)
Age range (years)
Family history of atopy (yes/no)a
Intermittent/mild persistent asthmab
Moderate/severe persistent asthmab
Intermittent/mild persistent rhinitisb
Moderate/severe persistent rhinitisb
Allergic sensitization to common pets
Allergic sensitization only to cat/dog
Age of onset of respiratory symptoms (years)
Passive smoke only
Yes (none for pets)
Possible modalities of exposure to pet allergens in 723 pet-sensitized patients (no and %)
Possible modalities of exposure to pets
DOG, no (%)
CAT, no (%)
DOG/CAT, no (%)
150 (20.75 %)
Direct domestic contact
213 (29.46 %)
Direct contact elsewhere
146 (20.19 %)
103 (14.25 %)
No apparent contact
111 (15.35 %)
Triggering of respiratory symptoms after exposure to pet allergens in 723 pet-sensitized patients (no and %)
Type of response
Total, no (%)
DOG, no (%)
CAT, no (%)
DOG/CAT, no (%)
Are allergic respiratory symptoms triggered by direct pet contact?
(*) All pets
Patients no (%)
Common pet ownership with a stable presence of the animal indoors is usually considered the main index of exposure to cat/dog, with the consequent risk of inducing allergic sensitization. “Are there animals at home?” is the common query administered by doctors to patients in order to collect information on anamnesis during epidemiological studies on the relationship between exposure to pets and development of allergic sensitization (e.g. during the first phase of life to evaluate a “protective effect” of early exposure to cat/dog). The same query is commonly used also in clinical practice to establish the clinical significance of a SPT positivity to cat/dog allergens and, thus, to manage the sensitized patients (pet-avoidance measures, allergen immunotherapy, pharmacological treatment of respiratory symptoms etc.). This commonly used question should not be considered the main factor of exposure to pet allergens and, consequently, the main risk factor for allergic sensitization either in clinical practice and large epidemiological studies [12, 20, 21]. In fact, Fig. 1 shows that only the condition b is reported usually in the questionnaires utilized for large epidemiological studies as well as in clinical practice for collecting data on anamnesis. In the conditions a, c and d the presence of a pet at home should be considered “formally negative” in the questionnaires or anamnestic report, but the level of direct/indirect exposure to pet allergens could be significant [4–7]. Only the condition e should be considered at the lower risk of pet allergen exposure after having excluded any direct/indirect contact with pets. Therefore, the simple answer “yes or no” on the question regarding the presence of pet at home can lead to misleading interpretation of the clinical significance of positive SPTs as well as the real risk of exposure to allergens of dog/cat in epidemiological studies. Consequently, we have previously suggested a new, more realistic, classification of modalities of exposure to pet allergens in “real life” based on the five possible conditions reported in Fig. 1. We have used this classification of exposure either for common pets and large animal such as horse, for which we have provided some specific modifications [10, 21–27]. To the best of our knowledge, this is the first study on the application of these new queries on the modality of exposure to pet allergens. As shown by Table 2, only a limited amount of patients sensitized to pets should be classified as “exposed to animals”, whereas the majority of patients should be classified as “not exposed” as a consequence of usual query “are there animals at home?. On the other hand and in agreement with our classification, a high percentage of formally “not-exposed” subjects were “really exposed” to pets. As a consequence of the present classification, only few patients were really “not-exposed” because no apparent direct/indirect exposure to pets or pet-derived materials. Another important finding of our study is that only half of our pet-sensitized individuals reported a clinically relevant symptoms worsening as a consequence of a close contact with pets, especially with cats. If we consider the modality of exposure, it is likely that these individuals belong to the groups directly exposed to pets at home or elsewhere . These findings confirm that in already pet-sensitized patients a direct and prolonged exposure to animals may represent a relevant risk factor for exacerbations of respiratory symptoms . It is important to note that 338 individuals (46.7%) failed to respond presumably because the symptoms were considered negligible, or not related with the contact of animals.
This is a possible limitation of this study. Other limitations are the lack of data on the presence of pet allergens at home for the reasons previously reported, and the lack of data on the general population regarding the exposure to pets in the first years of life.
GL conceived the idea, designed this study and wrote manuscript first draft. BG, BA, CM, CP, CE, CA, CMA, CMAR, DAM, FI, GF, GD, GDOM, MC, MM, MC, PG, PR, PA, PR, PF, SA, SP, SN, SB, SA, SG and VA recruited pet-sensitized patients. CL, RP, PG, collected the data and RM performed the statistical analyses. All co-authors drafted the manuscript and gave input and agreed to the final submitted version. All authors read and approved the final manuscript.
The authors would like to thank the veterinarian doctor Dr. Giovanni Menna as pet consultant and Mr. Gaetano Francesco Salzillo for technical assistance in the preparation of tables and figures.
Italian Allergic Respiratory Diseases Task Force (other components) Ilaria Baiardini, Caterina Bucca, Giorgio Walter Canonica, Maria Teresa Costantino, Stefano Del Giacco, Enrico Heffler, Stefania La Grutta, Vincenzo Patella, Erminia Ridolo, Giovanni Rolla, Oliviero Rossi, Eleonora Savi, Gianenrico Senna, Carlo Filippo Tesi, Giovanni Viegi.
The authors declare that they have no competing interests.
Availability of data
Data supporting our findings is stored on a database in the Department of Pulmonology, Haematology and Oncology. Division of Pneumology and Allergology. High Speciality “A. Cardarelli” Hospital, Naples Italy.
Ethics approval and consent to participate
Informed consent was obtained from the patients or their parents before performing skin prick tests in ambulatory settings. Ethics approval was not required because diagnostic tests have been carried out during routine outpatient activity.
No funding to declare.
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