Allergy-Like Asthma and Rhinitis

<i>Background:</i> Chronic idiopathic urticaria is considered an allergy-like skin disorder, and in some cases an auto-reactivity caused by mast cell degranulating factors has been demonstrated. A positive reaction to the autologous serum skin test (ASST), reflecting the presence of factors capable to degranulate the mast cells, is regarded as a reliable in vivo diagnostic test in chronic urticaria patients. About one out of three patients complaining for rhinitis or asthma does not show sensitization to any allergenic source. No data are available on the application of ASST to respiratory patients. <i>Methods:</i> A cohort of respiratory patients, aged 1 to 80 years, complaining about suspected respiratory symptoms was screened using a panel of inhalant allergens by means of SPT and IgE. Current and past information on skin and respiratory symptoms were recorded for each patient. Patients were divided in ‘allergy’ and ‘allergy-like’ whether or not they react to at least one allergenic source. Age and gender distribution were analyzed. A control group fulfilling criteria for chronic idiopathic urticaria (CIU) was selected as well. The ASST was applied to the control CIU group, to the allergy-like and allergy subsets, and to a group of 58 healthy adult subjects. <i>Results:</i> Allergy and allergy-like patients were differently distributed in relation to age and gender. Allergy-like children were prevalent before age six, whereas the prevalence of allergics steadily increased with age representing the large majority of patients in late childhood. The ratio of allergy/allergy-like subjects continues to increase in adult males, whereas adult females represent the large majority of the adult patients mainly within the allergy-like subset. Fifty-eight percent of CIU control patients reacted to the ASST. Among allergy-like patients ASST was positive in 47% of the adults (male 26%, female 54%), and in 84% of the children (no gender differences). The percentage of reactive subjects increased in the adult allergy-like subset if a CIU was associated (65%). Eighty-six percent of the pediatric patients and 61% of the adults having an allergy respiratory disease associated with an allergy-like condition had a positive ASST reactivity. Pure allergy patients reacted in 73% and 40% of the cases in the children and adults subgroups, respectively. Forty-five percent of healthy controls reacted to the ASST as well, and statistically significant gender differences were still recorded. <i>Conclusions:</i> An ASST reactivity is reported for the first time in allergy-like respiratory patients. A higher prevalence of reactive subjects has been recorded in all the pediatric subsets without gender differences, whereas female reactivity is prevalent among adults. The ASST reactivity seems to parallel the patient distribution within the entire respiratory cohort. Further studies are needed to demonstrate that the serum factors causing the ASST reactivity in respiratory patients are the same as for CIU affected subjects. In the light of recent in vitro findings, the ASST reactivity of healthy subjects could lead to a new interpretation of the autologous serum reactivity.