Out of Africa: what can be learned from the studies of allergic disorders in Africa and Africans?
OBJECTIVE
Allergic diseases have only recently gained serious attention in Africa. This review discusses recent studies that have focused on allergy among Africans and people of African ancestry.


RESULTS
Time trend studies of the prevalence of allergies in Africa show a consistent increase over a period of 7-10 years. Recent studies have reported that the link between IgE, skin reactivity to allergens and allergic symptoms increases with increasing gross national income of the country. Association between helminth infections, and allergies seem contradictory, which may be attributed to differences in the length of infection and species studied. Importantly, researchers have identified an 'urban diet' component, which is associated with increased skin reactivity to allergens. Finally, whereas Africans in rural Africa seem to suffer less from allergies, people of African ancestry in affluent countries have higher prevalence and greater severity of allergic symptoms than natives of these host countries, raising important issues on genetic control of allergic diseases.


CONCLUSIONS
Mechanisms underlying the development of allergy are a complex interaction of genetic susceptibility and environmental exposures. Identification of specific environmental factors, mechanistic pathways and genetic risk factors in sufficiently powered studies will be necessary to better understand and control the allergic march in Africa and elsewhere.
Obeng
Benedicta Baffoah
BB
Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands.
Hartgers
Franca
F
Boakye
Daniel
D
Yazdanbakhsh
Maria
M