Hi everyone - thanks for your comments. We'll try milk thistle, but we're still trying to identify what he is currently eating that's attacking his liver.
My daughter's horse developed photosensitivity on his legs last summer. Numerous bloodtests and 3 liver biopsies later we are still not very far forward! There was a slight infection which has been treated and no evidence of any obvious toxins. Yes , there was some liver damage though the liver...