Photosensitisation in horses causes severe sunburn-like reactions in unpigmented skin, and managing exposure to causative plants and UV light is central to preventing this painful condition.
Photosensitisation causes intense, acute welfare suffering — the combination of severe sunburn, weeping blisters, and secondary infection creates pain equivalent to significant burns injury. Affected horses may be extremely reactive to touching of the affected areas and may self-traumatise by rubbing. In severe cases, large areas of skin may slough. Secondary hepatogenous photosensitisation indicates liver disease that requires investigation and treatment in addition to skin management. Prevention is straightforward once the condition is understood — UV protection for white-skinned areas during summer and pasture management to remove causative plants. Treatment of established lesions requires pain management, wound care, and addressing any underlying liver disease.