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Study: exposure to sunlight can cause hair loss


#1

Is Androgenetic Alopecia a Photoaggravated Dermatosis?
Ralph M. Trüeb

Department of Dermatology, University Hospital of Zurich, Zurich, Switzerland

Dermatology 2003;207:343-348 (DOI: 10.1159/000074111)

Abstract

Progressive thinning of the scalp hair in androgenetic alopecia (AGA) results in a gradual decline in natural protection of the scalp from ultraviolet radiation (UVR). A number of pathologic conditions of the scalp are evidently related to UVR, particularly photosensitive diseases and disorders of the chronically photodamaged bald scalp. The most important chronic effects of UVR are photocarcinogenesis and solar elastosis. Besides these, erosive pustular dermatosis and ‘red scalp’ are distinct disorders peculiar to the balding scalp. While the consequences of sustained UVR on the unprotected scalp are well appreciated, the effects of UVR on hair loss have widely been ignored. However, clinical observations and theoretical considerations suggest that UVR may have negative effects: acute telogen effluvium from UVR has been described, and the production of porphyrins by Propionibacterium sp. in the pilosebaceous duct, with photoactivation of porphyrins leading to oxidative tissue injury, has been implicated in follicular microinflammation. Alternatively, keratinocytes themselves may respond to physicochemical stress from UVR, besides irritants and pollutants, by producing radical oxygen species and nitric oxide and by releasing proinflammatory cytokines, eventually leading to injury of the putative site of follicular stem cells in the superficial portion of the hair follicle. Since all of these processes involved in hair loss share the common feature that they are induced or exacerbated by exposure to sunlight, it is proposed that AGA is a photoaggravated dermatosis that requires photoprotection.


#2

Hairsite,

If this hypothesis were true, then women would go bald like men----------except that they dont

castrates would continue to go bald’

You’d lose hair on your forearms and face also.

The sun isn’t what causes baldness…your hair’s reaction to DHT does. Come on’, youve been at this too long to fall for this. Some things that make it into journals like Medical Hypothesis are pure crapola


#3

Unless there is support for that theory in statistics I must say I’m highly sceptical. Shouldn’t it be very obvious if one compared the prevalence of AGA in regions with different climate and different amount of natural sunlight? It shouldn’t be too difficult to compensate for genetic factors (race etc) in the statitics either.

So, does anybody know if there is statistical support for that idea? How common is AGA in say Canada, Scandinavia, (northern) Russia etc compared to countries closer to the equator, like southern Europe, southern USA, upper South America etc? And how much of the difference can be attributed to other factors?

EDIT: Oh, and what Benji said too. :slight_smile: