Hypersensitivity

Elsevier, Immunology and Allergy Clinics of North America, Volume 41, February 2021
Pollens are a major cause of seasonal allergic diseases. Weather may alter the production of pollens. Increased atmospheric temperatures lead to earlier pollination of many plants and longer duration of pollination, resulting in extended pollen seasons, with early spring or late winter. Longer pollen seasons increase duration of exposure, resulting in more sensitization, and higher pollen concentrations may lead to more severe symptoms. Climate changes in contact to pollens may affect both allergic sensitization and symptom prevalence with severity.
Elsevier, Journal of Allergy and Clinical Immunology, Volume 140, November 2017
The tremendous increase in allergy in the African continent cannot simply be explained by the change in public hygiene. There are many “prehygiene” communities with sewage-contaminated water supplies, helminth infestations, bare footedness, and poor housing, and still there is a high prevalence of allergic disease. Africans can be exposed to many risk factors facilitating severe asthma and wheezing, including airborne viruses, smoke, indoor dampness, cockroaches, and poor access to health care.