Itch: A Global Problem?

Abstract

Chronic itch (CI) is defined as itch occurring for 6 weeks and longer (1). Both the frequency and the causes of CI depend on age, predisposition like atopy, underlying diseases, ethnicity, climate/humidity, and especially access to the regional healthcare system (2-5). Different living conditions and rituals in human beings as well as migration also contribute to acute and chronic itch (5, 6). The prevalence of itch appears to differ worldwide (2, 3, 5). Direct comparisons between continents or countries are unusual and rare. There are only a few epidemiological studies on itch outside Europe and North America (2, 3, 5). This may be mainly caused by the facts that there is a lack of dermatological care in many countries, no direct access to a dermatologist in most countries, and several countries do not allow access to health care without any insurance certificate or cash payment. Comparing studies from different countries all over the world is difficult because of different and/or unclear, especially non-standardized definitions of itch, lacking to differentiate acute and chronic itch and especially of a lack of defining prevalence estimates. A very recent meta-analysis in atopic dermatitis (AD) and its clinical characteristics stated itch to be almost universally reported and the most common feature in AD (7). Chronic urticaria affects about 1% of the world population, presents with severe itch, and constitutes a global burden (8). Dermatological diseases (frequently accompanied by itch) have a worldwide distribution, but their prevalence is related to the geographical location. For example, otomycoses is much more frequent in subtropical and tropical climate (9) and does hardly contribute to the differential diagnoses of CI in countries with Western lifestyle. Scabies is considered to be the most frequent cause of acute itch but rather rare in CI. Scabies was recently added to the World Health Organization's list of neglected tropical diseases (NTDs), and its occurrence has been increasing in poor countries, countries with low standard of living, and especially in times of wars, migration, and in reception centers for asylum seekers (10). As infections and infestations are more prevalent in subtropical and tropical countries, scabies is a major cause of acute itch in these countries but is considered to be a less frequent cause in Western countries that are more affected by CI. All this may explain why itch is mentioned as a global burden of skin diseases, also in the elderly (11, 12). A large-scale implementation of a mass drug administration campaign of scabies in Ethiopia was called "stop the itch" (13).

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