Caraballo et al. World Allergy Organization Journal (2016) 9:20 DOI 10.1186/s40413-016-0110-7 REVIEW Open Access Particularities of allergy in the Tropics Luis Caraballo1*, Josefina Zakzuk1, Bee Wah Lee2,3, Nathalie Acevedo4, Jian Yi Soh2,3, Mario Sánchez-Borges5, Elham Hossny6, Elizabeth García7, Nelson Rosario8, Ignacio Ansotegui9, Leonardo Puerta1, Jorge Sánchez10 and Victoria Cardona11 Abstract Allergic diseases are distributed worldwide and their risk factors and triggers vary according to geographical and socioeconomic conditions. Allergies are frequent in the Tropics but aspects of their prevalence, natural history, risk factors, sensitizers and triggers are not well defined and some are expected to be different from those in temperate zone countries. The aim of this review is to investigate if allergic diseases in the Tropics have particularities that deserve special attention for research and clinical practice. Such information will help to form a better understanding of the pathogenesis, diagnosis and management of allergic diseases in the Tropics. As expected, we found particularities in the Tropics that merit further study because they strongly affect the natural history of common allergic diseases; most of them related to climate conditions that favor permanent exposure to mite allergens, helminth infections and stinging insects. In addition, we detected several unmet needs in important areas which should be investigated and solved by collaborative efforts led by the emergent researchgroupsonallergyfromtropicalcountries. Keywords: The Tropics, Allergy, Asthma, Rhinitis, Atopic dermatitis, Helminthiases, Papular urticaria, Anaphylaxis, House dust mite, Natural history, Allergens Background in temperate zones but important exceptions justify par- Allergy is an ecosystem determined disorder and variations ticular analyses. One of the most striking epidemiologic inriskfactorsandtriggersindifferentplacesisacommon differences is the perennial co-exposure to house dust finding. These variations can be grouped into two major mites (HDM) inhalation and helminth infections. The im- geographical environments that influence the evolution of pact of this context on the inception, expression, evolution allergic diseases: temperate zones and the Tropics. Now- and management of most allergic diseases is increasingly adays most of theoretical foundations of allergy are derived understood but basic and clinical research is still needed from studies in temperate zones but important emerging to have a more accurate view of the natural history of al- information from the Tropics is showing that there are lergic diseases in the Tropics. peculiarities in the natural history of allergies that deserve As allergies that are highly dependent on environmental more systematic studies, not only for scientific reasons but factors, it is expected that exposure to native (and some- also for designing strategies to improve the management times exclusive) allergenic sources contribute to a high pro- and prevention of these disorders. portion of the differences. However, there are other less In general, the prevalence of allergic diseases in the evident conditions that could modify allergy phenotypes in Tropics is as high as is observed in temperate countries the Tropics. The effects of parasitic infections and the and in some regions even higher; however, food allergies microbiota composition, which involve more complex and especially peanut allergy seem to be less common. It mechanisms that potentially alter the allergic responses is essential to know the particular and shared risk and even to the conventional inducers, are examples of these protective factors in order for the scientific community be conditions. In addition to specific tropical conditions, the able to stop the current allergy epidemic. Several risk fac- urban centers of the Tropics share several risk factors such tors for allergic diseases in the Tropics are similar to those as air pollution and culturally-unique dietary patterns. Because some of the current particularities in the Tro- * Correspondence: [email protected] pics are the result of limited hygiene conditions, it could 1Institute for Immunological Research, University of Cartagena, Cra. 5 # 7-77, Cartagena, Colombia be said that when future sanitary standards become the Full list of author information is available at the end of the article © 2016 Caraballo et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Caraballo et al. World Allergy Organization Journal (2016) 9:20 Page 2 of 44 same as in the industrialized world, the differences would conditions favor the existence of house dust mites and in- be determined basically by genetic factors, differences in testinal helminth infections, two of the most important microbiota due to natural climate and biodiversity, and environmental components of allergic diseases in the Tro- currently unknown factors influencing the immune re- pics. In general, the temperate zone has moderate climate sponses in the Tropics. In this review we present and and four seasons but there are variations such as oceanic, analyze the results of a comprehensive search of the inter- Mediterranean and hemiboreal climates. In the Tropics national and regional scientific databases, looking for those there are also places of high altitudes where the climate is aspects of allergy in the Tropics that, based on scientific not typically hot and humid. These internal geographical evidence, could be considered different from those ob- variations in both zones could be the source of epidemio- served in places with temperate climates. The literature logical differences, but in this review each zone will be search was conducted mainly in Pubmed and the search taken as a whole. terms were selected according to the topics, for example, “asthma symptoms” and “allergen sensitization”.These Cultural beliefs and "folk medicine" were combined with “”tropical climate” or “tropics”, “Asia”, In tropical countries high rates of uncontrolled asthma “Africa”, “South America”, etc. MeSH terms were also used and other allergies are frequently observed [1, 2], which and limited, for example, to “humans”, “English language”, is related to the particularities in perception and cultural etc. Most searches were accessed during 2015. The search attitudes towards disease, as well as education and socio- results were then reviewed and selected based on basic, epi- economic conditions. The use of folk medicine (also demiological or clinical relevance and studies done in the known as traditional or indigenous medicine) to alleviate tropical and subtropical regions. The investigation was symptoms of asthma is well-accepted among different done to provide updated information to investigators and tropical cultures, but one concern about disease manage- clinical practitioners and to evaluate the following hypoth- ment with this type of medicine is that it reduces adher- eses: a) Allergic diseases in the Tropics have particularities ence to allopathic drugs that have been scientifically tested that deserve systematically designedstudiesanddescription for allergic symptoms. While this theme has not been suf- in order to detect unmet research needs and provide better ficiently addressed, there are many reasons to think that management of patients in the Tropics. b) Most of the par- the poor use of the optimal treatment for allergic diseases ticularities are related to climate conditions that favor the has a socio-economical origin rather than a cultural pref- permanentexposuretomiteallergens, helminth infections erence of folk medicine by people living in the Tropics. and stinging insects. Studies about cultural beliefs regarding asthma in "La- tino" communities show the co-existence of the biomed- The Tropics: particular climate and socio economic ical model and ethnocultural beliefs to explain disease. conditions influencing allergy Closeness to allopathic medicine is dependent on access Climate and biodiversity to the health system, with the poorest being more at- The Tropics (Torrid Zone) is one of the most dynamic tached to alternative options for treatment and health at- and interesting regions of the world and contains the tention [3]. Qualitative research conducted in Latino largest collection of living plants and animal species. The communities also suggests that, in spite of using folk medi- historical view that inhabitants from the temperate zone cine products, parents or caregivers do not replace allo- had about the Tropics has changed from not suitable for pathic drugs for asthma treatment [4, 5]. In contrast, civilized habitation to being a paradise that harbors most of Bearison et al. found that, for Puerto Ricans, for example, planet’s biodiversity which should be protected for the sake reliance on home remedies for asthma is related to poor of humanity. For example, the Amazon rainforest covers adherence with prescribed regimens [6]. most of the Amazon Basin of South America