Comparison of allergens and symptoms in patients with allergic rhinitis between 1990s and 2010s

A total of 2722 patients between January 1994 and December 1994 (representing the 1990s) and 4980 patients between January 2010 and December 2014 (representing the 2010s) completed the same questionnaire when they underwent a skin prick test (SPT) at the Asan Medical Center, a tertiary care center in Korea, for an AR diagnosis. Patients with rhinitis were referred to our center when primary or secondary clinics across Korea were unable to adequately treat rhinitis symptoms. The proportion of patients in our hospital living in Seoul and other urban, suburban, or rural regions corresponds to the proportion of Koreans living in Seoul and other regions. All patients had a suggestive clinical history of AR with at least two of the following symptoms: recurrent nasal obstruction, rhinorrhea, sneezing, and itching of the nose/eye with no history of acute upper airway infections. The questionnaire was completed either by the patients themselves (if aged > 14 years) or by their caregivers (if aged ≤ 14 years). This study meets the ethical principles of the Declaration of Helsinki and was approved by the Institutional Review Board of Asan Medical Center (2017-1402), which waived the requirement of patient consent.

The study included 1447 of the 2722 patients from the 1990s and 3388 of the 4980 patients from the 2010s with positive SPT results. Patients were diagnosed with AR if they had at least two of the abovementioned symptoms and positive SPT results. The mean age of the 1990s patients was 24.3 (range 3–72) years and that of the 2010s patients was 33.6 (range 3–84) years.

Standardized allergen extracts (Bencard Allergie, München, Germany) including house dust mites (Dermatophagoides pteronyssinus [Dp], D. farinae [Df]), cat fur, dog dander, Alternaria, Aspergillus, cockroach, mixed grass pollen, mixed tree pollen, ragweed, and mugwort were used. Histamine and saline were used as positive and negative controls, respectively. If the patients were taking antihistamines, the dose was discontinued for at least a week before conducting SPT. SPT was performed on either or both forearms, depending on patient age. The distance between any two allergens was maintained at 2 cm to avoid cross-contamination. A wheal diameter measuring > 3 mm indicated a positive response to the allergen.

The questionnaire designed by the authors consisted of the following items: symptoms, the season with the most severe symptoms, the time of the day with the most severe symptoms, and aggravating factors for the symptoms.

Dp and Df were the most common allergens in both patient groups. However, the proportions of positive SPT results for Dp and Df were significantly higher in patients from the 2010s than in those from the 1990s (P = 0.016 and P = 0.022, respectively). In addition, the proportions of positive rates for tree pollen as well as those for indoor allergens such as cockroach, Aspergillus, and Alternaria were significantly higher in patients from the 2010s (P < 0.05 for each). In contrast, the proportions of positive results for cat fur was lower in patients from the 2010s than in those in the 1990s (P < 0.001) (Table 1).

The proportion of polysensitized patients was significantly higher in the 2010s (59%) than in the 1990s (55.6%) (P = 0.030). Most patients who were sensitized to pollen in both the 1990s and 2010s showed a positive response to other allergens such as Dp, Df, cat fur, dog hair, cockroach, Aspergillus, and Alternaria. However, the proportion of patients sensitized only to pollens was significantly lower in the 2010s (6.8%) than in the 1990s (10.5%) (P < 0.001).

The male-to-female ratio of AR patients significantly increased, from 1.41 (847:600) in the 1990s to 1.78 (2169:1219) in the 2010s (P < 0.001). In the 1990s, AR prevalence was the highest in patients aged 10–19 years (29.8%) and gradually decreased with age. In contrast, in the 2010s, the prevalence was the highest in patients aged 20–29 years (23.1%) and 10–19 years (21.1%), gradually decreasing and then increasing again in those aged 50–59 years (15%) (Fig. 1).

The most common symptom was nasal obstruction, followed by rhinorrhea, sneezing, and itching in patients from both the 1990s and 2010s (Table 2). In the 2010s, the proportion of rhinorrhea was slightly lower than in the 1990s (P = 0.030), whereas the proportion of itching was higher (P < 0.001). When the severity of major symptoms was compared between the 1990s and 2010s, the proportions of moderate-to-severe nasal obstruction and itching were higher in the 2010s, whereas that of rhinorrhea was lower and that of sneezing remained unchanged (Table 3). Among minor symptoms, the rates of olfactory disturbance, cough, sore throat, and fatigue were significantly higher in the 2010s than in the 1990s (all P < 0.01, Table 2). In patients allergic to Dp, Df, cat fur, dog dander, and tree pollen, the most common symptoms were nasal obstruction, followed by rhinorrhea, sneezing, and itching. The proportions of nasal obstruction, rhinorrhea, and sneezing did not differ between the 1990s and 2010s, whereas the proportion of itching was higher in the 2010s than in the 1990s (Table 4). However, the proportions of symptoms severity based on allergen differed between the 1990s and 2010s. The proportions of moderate-to-severe nasal obstruction and itching in patients allergic to Dp, Df, cat fur, and dog dander were higher in the 2010s than in the 1990s. The proportion of moderate-to-severe rhinorrhea in patients allergic to Dp and Df was lower in the 2010s than in the 1990s and that of moderate-to-severe sneezing in patients allergic to Dp, Df, cat fur, dog dander, and tree pollen did not differ between the 1990s and 2010s (Table 4).

Patients experienced the most severe symptoms during seasonal changes, followed by throughout the year and winter in both the 1990s and 2010s (Table 5). When compared with the 1990s, reported symptom severity increased during seasonal changes (P < 0.001), decreased throughout the year (P = 0.003), and remained unchanged during individual seasons (P > 0.05) in the 2010s. The time of the day with the most severe symptoms was the morning, followed by throughout the day in both the 1990s and 2010s. In the 2010s, the proportion of patients who reported the most severe symptoms throughout the day was significantly higher than that in the 1990s (P < 0.001). However, reports of severity in the morning were lower in patients from the 2010s than in those from the 1990s (P < 0.001).

Dust and cold air commonly aggravated AR symptoms in patients both from the 1990s and 2010s (Table 6). Symptom aggravation due to cleaning, dust, bedding, and air conditioning was more common in the 2010s than in the 1990s (all P < 0.001).