Hypericum perforatum (perforated St John's wort, common St John's wort, millepertuis). Related species: H. crispum, H. calycinum (rose of Sharon, St John's wort). A member of the plant family HYPERICACEAE. Herbaceous plant with dense foliage; the leaves and stems contain small secretory glands which produce a translucent chlorophyll-free oil with a balsamic odour. The plant has large conspicuous, cup-shaped yellow flowers with prominent stamens; the fruit are ovoid capsules containing black seeds.


[affected.gif] Animals most affected
Sheep (cattle, horses).


[etiology.gif] Etiology
Ingestion through grazing or consumption of fresh cuttings or contaminated hay or fodder.


[toxic.gif] Toxicity
Contains hypericine, a red fluorescent pigment responsible for causing primary photosensitization in animals. The entire plant is toxic, particularly the flowers. Drying the plant does not modify significantly its toxicity. Toxic doses not known.


[clinical.gif] Clinical features
There is a latent period between ingestion of the plant and manifestation of clinical signs, varying from several hours to several days. The effects occur exclusively when the animal is exposed to sunlight.

General effects

Gastrointestinal effects

Local effects


[lesions.gif] Lesions


[treatm~1.gif] Treatment
No antidote. Symptomatic and supportive care only: