St John's Wort and the use of Hypericin
Dave Poole

St. John's Wort - Hypericum perfoliatum is an attractive, small to medium-sized, semi-woody herb bearing terminal panicles of bright yellow flowers from early summer onwards. Native to Europe, it has been introduced either deliberately or accidentally, to many countries throughout the world and can rapidly colonize vast tracts of suitable terrain. Extracts from the leaves and flowers have long been used in the treatment of a bewildering range of ailments from bedwetting to skin allergies, however the active constituent - Hypericin, is primarily used as a mild anti-depressant and it is claimed to have similar qualities - albeit less pronounced, to Prozac. Superficially, Hypericin would appear to be a beneficial compound in the treatment of certain types of depression in humans. Side effects and toxicity have been demonstrated to be very low in comparison to more conventional remedies and there have been no recorded instances of fatality as a result of its use.

In recent years, there have been occasional recommendations for Hypericum in the treatment of birds which have become habitual feather pluckers. Certainly, hypericin is far less problematic and severe compared to certain drugs such as halipedol however, it has been demonstrated that hypericin increases sensitivity to sunlight - marginally in humans, but markedly so in animals such as sheep. Sheep browsing upon Hypericum perfoliatum in Australia have been killed as a result of dramatically increased sensitivity to sunlight (phototoxism) and there, the plant is classed as a noxious weed as a result. In humans, increased photosensitivity diminishes markedly when hypericin is discontinued, but little or no research has been carried out as to any possible long term effects (if any) in animals.

The use of hypericin in avian medicine may pose problems owing to the fact the parrots in particular need appreciable amounts of natural light in order to synthesise Vitamin D. Any drug or compound which increases photosensitivity is liable to cause severe problems in this respect and hypericin cannot be considered as a safe 'long term' treatment for psittaciness. Little or no work has been carried out to ascertain the full effects of hypericin in parrots and the possibility of phototoxism cannot be ruled out. As a precaution, any birds which are being treated with hypericin, should not be exposed to bright, natural light during medication and they should be kept in shaded conditions for at least 7 days following the final treatment.