The prevalence of allergic diseases is dramatically increased in the last decades. Some factors are believed to contribute to that phenomenon i.e., more affluent and urbanized society, increased outdoor and indoor pollution, changes in life style and dietary habits, climate change and reduced biodiversity [1]. Allergies now affect up to 30% to 40% of the population worldwide with the children and young adults bear the greatest burden of these diseases as the escalation of the prevalence of the diseases is mostly seen in these populations [2]. But there is a wide variation in the prevalence of allergic diseases between developed and developing countries, being lowest in the later [3]. Allergy which includes asthma among the urban population is considered to be related to westernized life style [4]. While rural population in the developing countries are more exposed to environmental microorganisms which protect them from allergy and atopy [56].

Indonesia has the lowest prevalence of asthma, allergic rhinitis, and eczema symptoms as showed by the results of The International Study of Asthma and Allergies in Childhood (ISAAC) in 2007 [378]. Surabaya is the second biggest city in Indonesia, but unfortunately was not involved in the ISAAC study. The fast economic growth in Surabaya give rise to the increasing number of city inhabitants which in turn contributes to growing numbers of cars, motorcycles, and creates high levels of air pollution. Many areas in the city can no longer support the requirements of the people and become slump areas. This condition presents a unique situation where air pollution and the low hygiene and sanitation have an opposing influence on the pathogenesis of allergic diseases [910]. To date, the prevalence of allergic sensitizations and diseases among Surabaya's school children and undergraduate students are unknown. A cross-sectional epidemiologic study was conducted to respond to the following questions: (1) what is the prevalence of allergen sensitization (defined as skin prick test [SPT] positivity) and allergic diseases among school children and undergraduate students in Surabaya, and (2) what are the common types of allergen sensitizations and allergic diseases in these populations.

There was a trend of increasing allergic sensitization among school children and undergraduate students, being 21.9% among primary school children (aged 7 to 12 years), to 28.9% among secondary school children (aged 13 to 18 years), and to 45.3% among undergraduate students (aged >19 years) as in Fig. 1.

The distribution of skin test positivity for all allergens tested on the respondent is shown in Table 1. Among 28 primary school children with positive skin test, the most common sensitization was against cockroach, fungi/mold spore (both at 42.8%), house dust mites (28.6%), grass pollen (17.9%), and crab (14.3%). Among 64 secondary school children with positive skin test, the most common sensitization was against house dust mites (62.5%), followed by cockroach (37.5%), fungi/mold spore (28.1%), grass pollen (23.4%), and crab (21.9%). While among 68 undergraduate students with positive skin test, the most common sensitization was against house dust mites (58.8%), followed by cockroach (47.1%), crab (41.2%), fungi/mold spore (36.7%), and grass pollen (20.6%) (Fig. 2).

The information from the personal history prevails 278 respondents suffered from at least one allergic disease manifestations. The most common allergic disease found was allergic rhinitis (23.0%), followed by asthma (6.8%), food allergy (3.4%), and atopic dermatitis/eczema (1.8%) (Fig. 3). A substantial number of respondents actually suffered from urticaria (20.6%) but this data was not shown in Fig. 3 because this diagnosis category was not assessed in the ISAAC study.

Table 2 shows some factors (allergic disease inheritance, home and environmental allergen exposure) that may predispose the study respondent to allergic diseases. Out of 278 respondents with allergic disease manifestation, 169 (60.8%) had at least one of the parents (father, mother, or both) suffered from any allergic disease.

This study showed a trend of increasing prevalence of skin test positivity among school children and students with the increasing age (from primary school children to undergraduate students). It gives an indication that although Indonesia belongs to the developing countries, the prevalence of allergic diseases in school children and undergraduate students of metropolitan cities such as Surabaya shows a pattern more similar to that of the developed countries [16171819].

The most common allergic disease in this study was allergic rhinitis, as prevailed at 23% is within the estimation for the worldwide (10%–30% of the population) but lower as compared to that of similar population-based study in the Netherlands [16], Finland [17], Australia [18], or United States [19]. Compared to other cities in the South East Asian region, the rates in Surabaya were found to be higher than in Kota Bahru (Malaysia) [20] or Taoyuan (Taiwan) [21], but similar to metropolitan cities as Bangkok (Thailand) [22], or Metro Manila (Republic of The Philippines) [23]. Consistent to the results from those big cities and that of developed countries, the prevalence of asthma and atopic dermatitis/eczema in this study was also lower than the allergic rhinitis [1617181920212223].

The present results were apparently higher than the previous reported prevalence for Indonesia in ISAAC study in 1998 [3]. According to the survey held in Bandung at that time, the estimate prevalence of allergic rhinitis in Indonesia was around 5% [3]. There are several factors that may explain the increasing prevalence of allergic diseases in Surabaya. Genetic factors within populations, such as atopy (history of allergic disease inheritance in the family), usually do not change in a decade, so researchers have postulated other causes from the environment for the increased prevalence of allergic diseases [24]. These include the so-called 'hygiene hypothesis,' which refers to a lack of immunological shift from Th2-dominant, infantile states to Th1-dominant, adult type responses during the early period of life as a result of decreased exposure to microbial antigens [1925]. Other researchers also mentioned the important role of extrinsic antigens, including air pollution [262728].

In accordance with the current concepts of the immunopathogenesis of allergic disorders [10], the majority of our study respondent with allergic disease manifestations had parental atopy. Most of them were also born as first child, and admitted the exposure of house dust mites allergens in their home or environment. There was a decreasing percentage of allergic disease from the first child to second child, to third child and so on. Pet ownership does not seem to have an effect. Most of the respondent claimed that they lived in clean and hygienic house and environment (data was obtained as a self-testimony from the interview and the exact conditions were not verified), but from the facts that cockroach and fungi/mold spore were found to be the common allergens among these children, we suspected that they live in damp houses with many food leftovers that might attract cockroach into their house.

Other factors may also play a role, such as decreased microbial exposure and the increased air pollution. With regards to the decreased exposure to microbial antigens, recent data on the use of antibiotics by doctors in Indonesia gave a strong supporting evidence [29303132]. Irrational use of antibiotics has become a common practice in developing countries, where the prevalence of infectious disease burden is aggravated by uncontrolled access to antibiotics. Twenty years ago, a survey in Jakarta revealed that doctors prescribed antibiotics to 94% of young children although they admit that the infection was of viral origin [2930]. This practice did not change much to the present days as was shown by the results of The Antimicrobial Resistance in Indonesia ‘Prevalence and Prevention’ study held in Surabaya and Semarang [31]. Being less than 18 years of age and uninsured were independent determinants of antibiotic use. Furthermore, antibiotics without prescription can even be obtained over the counter in pharmacies and drug stores, although this has been prohibited by law [3132]. Urban provenances, being adult, male sex, and having no health insurance were independent determinants of antibiotic self-medication [3132]. This practice seemed so overwhelming in all areas of the city, and in that way might undo the protective effects of living in slump areas with unhygienic sanitation.

The role of air pollution in the rising trends in allergic respiratory diseases had been emphasized by the results of both epidemiological and laboratory studies [262728]. Pollutants of particular interest include nitrogen dioxide, diesel exhaust particles, as well as particulate matter [33]. Two major mechanisms that may explain the phenomenon is allergic sensitization and airway hyper-responsiveness induced by increased fossil fuel combustion. Airway hyper-responsiveness to environmental allergens may subsequently aggravate symptoms of allergic rhinitis [33]. A longitudinal birth cohort study reports that children living near major roads have increased odds of runny nose and sneezing during the first year of life as well as increased odds of sensitization during the first 8 years of life [2634]. Stronger associations appeared between traffic-dense areas and respiratory symptoms among children living in poverty [35]. These arguments fit to the current condition in Surabaya where people (including children and students) are trapped in heavy traffic at morning and evening rush hours every day.

The major limitations of this study were the cross-sectional design and the use of questionnaires to obtain information on risk factors. The cross-sectional design does not allow us to identify the temporal sequence between the risk factors and allergic diseases or atopy, although reverse causality is not a possibility for many of the exposures measured. The use of questionnaires makes the study open to information bias. Misperception of allergen and microbial antigens exposure is likely to be a problem with this study as we did not observe directly the housing and the surrounding environmental condition of the study respondent. However, due to this study was population based, the findings can likely be generalized to the population of school children and undergraduate students living in metropolitan cities like Surabaya in Indonesia or to similar areas elsewhere in the region.

In conclusion, the present study has shown the prevalence of allergen sensitizations and allergic diseases in school children and undergraduate students in Surabaya are markedly higher than the previous estimates. This information provides a suitable baseline for the analysis and the anticipation of potential health problems among children and young adults in the future, which hopefully lead to a proper health care and health intervention planning to deal with the increasing prevalence of allergic diseases. There is also an urgent need for an in-depth study to define epidemiological factors that responsible for this increase.