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*cattle and sheep

*sharply confined to the unpigmented areas of the skin

Photosensitisation is a condition of the dermis caused by a reaction induced by photodynamic agents (PDAs) exposed to UV light in the skin of animals that have eaten certain plants. Photosenstisation is primarily a condition of sheep, cattle and horses but other species may also be susceptible.

*occurs as a result of the effect of strong sunlight

Photosensitisation can be divided into two categories; primary and secondary photosensitisation). Primary photosensitisation occurs due to the normal ingestion of growing lush green plants containing PDAs. Secondary (hepatogenous) photosensitisation occurs as a result of liver or bile duct damagem, leading to accumulation of phylloerythrin in the blood, body tissues and skin due to insufficient conjugation and excretion by the liver.

 

The condition is characterised by 'sunburn-like' lesions that are confined to unpigmented areas of the skin

**due to the effect of UV light on a photodynamic agent (PDA) present in the skin, such as is '''phylloerythrin''' derived from chlorophyll

**due to the effect of UV light on a photodynamic agent (PDA) present in the skin, such as is '''phylloerythrin''' derived from chlorophyll

**therefore, the disease occurs mostly in those animals consuming large quantities of grass

**therefore, the disease occurs mostly in those animals consuming large quantities of grass

**corticosteroid induced

**corticosteroid induced

 

 

 

*hepatogenous photosensitisation

*hepatogenous photosensitisation

**chlorophyll is metabolised to '''phylloerythrin'''

**chlorophyll is metabolised to '''phylloerythrin'''