Particularities of allergy in the Tropics

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 research groups on allergy from tropical countries.Electronic supplementary materialThe online version of this article (doi:10.1186/s40413-016-0110-7) contains supplementary material, which is available to authorized users.

Intradermal immunotherapy with low-dose house dust mite allergens in patients with allergic rhinitis: A proof-of-concept study

“…3,4 A well-known unique feature of AIT is the modifi cation of the natural course of allergic diseases, inducing sustained long-term eff ects persisting years beyond treatment discontinuation. 2,3,5 In tropical/subtropical areas of the world with high levels of relative humidity all year round, domestic mites are main sources of sensitization; 6,7,8,9,10,11 perennial symptoms prevail and pollinosis, for the most part, is a non-relevant clinical issue. 9,10 High dose aqueous subcutaneous immunotherapy (SCIT) is a validated and eff ective route of allergen administration for the house dust mite (HDM) as for pollen allergies.…”

The tropics, helminth infections and hygiene hypotheses

“…In the tropics, a gradient can be detected from rural communities, heavily parasited and exhibiting less allergic symptoms [18], to urban settings less exposed and light parasited where the effect of the helminthiases is predominantly IgE/ Th2 enhancer [19] and allergic diseases are as frequent as in industrialized societies and have even increased during the last decade [1]. An additional relationship between helminth and allergy is found in developed wealthy countries where there is no parasite-derived immunoregulation [12].…”

“…Therefore, in the tropics, the analyses cannot be simplified assuming that the prevalence of allergic diseases is low or claiming that conditions potentially preventive of allergy are missing. Indeed, in this zone, all factors whose absence or presence are supposed to determine the increase of allergy concur; however, the increasing frequency trends of asthma and rhinitis are also observed [1]. Here the roles of helminth infections on these trends are analyzed, taking for granted that several factors should be considered under the umbrella of more than one working hypothesis.…”

Mite allergens

“…There are more than 30 clinically relevant mite species; two of them Dermatophagoides pteronyssinus (Pyroglyphidae family) and Blomia tropicalis (Echimyopodidae family) are widely distributed [2,6]. Since each of them has at least 20 IgE-binding components (Der p 1 to Der p 30 and Blo t 1 to Blo t 21, isoforms not included), in tropical places it is possible to be exposed to a variable number of epitopes from at least 40 potential allergenic components from mites.…”

“…They are also risk factors for rhinitis [2] and food-induced anaphylaxis [3]. Some other potential activities have been suggested for HDM or their components, for example, oxidative damage to proteins, lipids, and DNA in lung cells [4] or induction of gastrointestinal inflammation by the enzymatic properties of Der p 1 [5].…”