Changes

primarily a condition of sheep, cattle and horses but other species may also be susceptible.  

primarily a condition of sheep, cattle and horses but other species may also be susceptible.  

The condition can be divided into two categories; primary and secondary. Primary photosensitisation occurs due to the ingestion of lush green plants containing photodynamic agents such as St John's Wort or clover. Secondary (hepatogenous) photosensitisation is the most commmon type of photosensitivity seen in animals and occurs as a result of liver or bile duct damage, most often due to ingestion of hepatotoxic plants such as Ragwort. Due to insufficient conjugation and excretion by the liver, the photosensitising agent phylloerythrin (a breakdown product of chlorophyll) accumulates in the blood, body tissues and skin. This leads to absorption and release of UV light, resulting in a phototoxic reaction.

The condition can be divided into two categories; primary and secondary. Primary photosensitisation occurs due to the ingestion of lush green plants containing photodynamic agents such as St John's Wort or clover. Secondary (hepatogenous) photosensitisation is the most commmon type of photosensitivity seen in animals and occurs as a result of liver or bile duct damage, most often due to ingestion of hepatotoxic plants such as Ragwort. The normal conjugation and excretion of Phylloerythrin (a breakdown product of chlorophyll) is prevented and it therefore accumulates in the blood, and body tissues. In the skin this leads to the absorption and release of UV light, resulting in a phototoxic reaction.

==Clinical signs==

==Clinical signs==