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Use of the sun for therapeutic purposes is described in numerous ancient manuscripts. After disappearing during the Christian era, heliotherapy began being used again at the beginning of the 19th century when artificial sources of ultraviolet light (UV) made their first appearance. Its value was very rapidly recognised with the Nobel Prize in Physiology or Medicine being awarded to Niels Finsen in 1903 for the treatment of lupus vulgaris with a carbon arc lamp.
Studies in physics and biology led to scientists rapidly understanding that the benefits of natural heliotherapy could be attributed to UV radiation in the natural spectrum and phototherapy became a synonym for the therapeutic use of UVs.
Broad spectrum UVB phototherapy was really born when the efficacy of a mercury-vapour lamp used alone to treat psoriasis (Alderson) or potentiated by tar (Goeckerman, 1925 and Ingram, 1953) was discovered.
A decisive step was made in phototherapy in 1974 with trials involving the treatment of psoriasis by oral administration of psoralen followed by exposure to newly-developed fluorescent tubes giving off high-energy UVA radiation . A new type of phototherapy was born, referred to by the initials Psoralen UltraViolet A (PUVA) therapy, tremendously increasing the popularity of phototherapy for the treatment of dermatological conditions.
At the beginning of the 1990s, the development by industrialists of new UVB tubes with very narrow spectral output and an emission peak at about 311 nm (Philips TL01) led to a new type of phototherapy, referred to as UVB narrow spectrum phototherapy (as opposed to standard broad spectrum UVB therapy). This type of phototherapy was first used to treat psoriasis because previous studies had demonstrated that the optimal wavelengths for treatment psoriasis were around 311 nm.
At the beginning of the 1990s, German teams proposed the use of high intensity, mostly long-wave UVA radiation (340-400nm), also referred to as UVA1 radiation, to treat atopic dermatitis. This method referred to as UVA1 phototherapy was essentially developed in Germany for the treatment of atopic dermatitis, but like PUVA therapy, it was also tried empirically for the treatment of various other skin dermatoses.
Use of UVA1 phototherapy treatment units comprising several lamps joined in series with a sophisticated cooling system for very high-intensity irradiation of the body (130 joule of UVA1 per session) is not very widespread in France. The method will not be described in any detail in this paper, the principal purpose of which is to describe PUVA therapy and UVB phototherapies.
Finally, more recently still, trials have been performed with UVB excimer lasers for the treatment of psoriasis plaques [2, 3] and vitiligo , and with a novel 308-nm monochromatic excimer light delivery system (Excilite®; DEKA, Florence, Italy) for the treatment of various dermatoses usually treated by UVB TL01 [5,6]. The results obtained with these systems are too segmented to really appreciate whether these new UVB phototherapies have their place in current treatment strategies in terms of feasibility, cost, efficacy and risk compared to other phototherapies and particularly compared to phototherapy alternatives. Consequently, these methods will not be described in this paper.
Dynamic phototherapy, phototherapy for acne and neonatal jaundice which use visible radiation, and extracorporeal photochemotherapy (genuine ex vivo PUVA therapy), which in the strict sense is closer to cell therapy than to skin phototherapy, also fall outside the scope of this paper.
The indications for phototherapy, determined following initial convincing studies carried out on psoriasis in most cases, were established in purely empirical studies. The mechanisms of action of this type of treatment were paradoxically investigated at a later stage and to date, have only partially been understood.
A multitude of dermatoses are now treated by phototherapy and clinical trials comparing various techniques have enabled the indications of each method to be more clearly defined.
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