Plants causing liver disease and photosensitization (sensitivity to sunlight) are often grouped together. Photosensitization is often, but not always, a secondary symptom of liver disease caused by poisonous plants.
As chlorophyll breaks down, it becomes phylloerythrin, a phototoxic compound. In healthy animals, the liver filters phylloerythrin from the blood, preventing any damage. If the liver is compromised by toxins, it is unable to remove the compound from the blood and photosensitization occurs.
Some plants contain compounds that, once absorbed into the bloodstream, react to UV exposure, without any effect on the liver. Photosensitization resembles severe sunburn. Plants from a variety of families can impact liver health or cause related nutrient deficiencies. Photosensitization symptoms are most significant on white skinned animals or white skinned portions of animals, around the face, and near hooves.
Common pasture plants affecting the liver and blood and/or causing photosensitization:
- Alliums pp. (Onion)
- Descuriania sophia (Flixweed/Tansy mustard)
- Equisetum spp. (Horsetail and Scouring rush)
- Hypericum perferatum (St. Johnswort)
- Pteridium aquilinum (Western bracken fern)
- Thermopsis rhombifolia (False lupine)
- Tribulus terrestris (Puncture vine)
- Trifolium spp. (Clover)
- Vaccaria pyramidata (Cowcockle)
- Xantium strunarium (Cocklebur)