Urticaria is one of the most common dermatological conditions with diverse clinical presentations and causes. Solar urticaria (SU) is a rare subset of physical urticaria, where symptoms are induced by direct exposure of the skin to sunlight. As little as 5 minutes of sun exposure can cause flares and whealing on exposed skin sites, accompanied by severe itching. The wavelengths of radiation causing the eruption (i.e. the action spectrum) are in the ultraviolet or visible light range. Initially described by Merklen in 1904, SU may have a very sudden and dramatic onset, and then rapidly disappear once the exposure ceases. A delayed form of SU has also been reported, although this is extremely rare. Information on the pathophysiology of SU is limited and symptoms are confined to areas of the body exposed to direct sunlight. The condition can be very distressing and severely impair the individual's ability to go outdoors and to tolerate indoor lighting. The standard therapy, i.e. oral antihistamines, is only partially effective and may provide little worthwhile relief of symptoms. This pilot study is proposed to evaluate implants containing 16mg CUV1647 as a prophylactic treatment for patients with SU. The effectiveness of CUV1647 will be assessed by determining the minimum urticarial dose before and after treatment.

When human skin is exposed to ultraviolet radiation from the sun or via the use of solaria, it responds by increasing melanin levels within epidermal melanocytes. Ultraviolet light enhances the local production and release of alpha-melanocyte stimulating hormone (alpha-MSH), which results in increased melanin levels through a process known as melanogenesis. Melanin, in the form of eumelanin, is a photoprotective agent. The mechanisms proposed for photoprotection include, but are not limited to, the absorption and scattering of UV and visible radiation, free radical scavenging and quenching of UV light. There is also increasing evidence that melanogenesis represents a major antioxidant defence mechanism in melanocytes, neutralising the deleterious effects of free radicals and active oxygen species. Eumelanin acts as a neutral density filter and, unlike most sunscreens, reduces all wavelengths of light equally so that the photoprotection provided by epidermal melanin pigmentation is essentially independent of wavelength. CUV1647 (\[Nle4-D-Phe7\]-alpha-MSH) is a potent and longer lasting analogue of alpha-MSH which stimulates the production of eumelanin in the skin without the specific cell damage that usually occurs when melanin production is stimulated by UV radiation. Urticaria is one of the most common dermatological conditions with diverse clinical presentations and causes. Solar urticaria (SU) is a rare subset of physical urticaria, where symptoms are induced by direct exposure of the skin to sunlight. As little as 5 minutes of sun exposure can cause flares and whealing on exposed skin sites, accompanied by severe itching. The wavelengths of radiation causing the eruption (i.e. the action spectrum) are in the ultraviolet or visible light range. Initially described by Merklen in 1904, SU may have a very sudden and dramatic onset, and then rapidly disappear once the exposure ceases. A delayed form of SU has also been reported, although this is extremely rare. Information on the pathophysiology of SU is limited and symptoms are confined to areas of the body exposed to direct sunlight. The condition can be very distressing and severely impair the individual's ability to go outdoors and to tolerate indoor lighting. The standard therapy, i.e. oral antihistamines, is only partially effective and may provide little worthwhile relief of symptoms. This pilot study is proposed to evaluate implants containing 16mg CUV1647 as a prophylactic treatment for patients with SU. The effectiveness of CUV1647 will be assessed by determining the minimum urticarial dose before and after treatment.