Clinical Applications
Clearly, the potential scope of clinical application of St. John's wort is extensive. However, if one narrows the focus down to those activities that are most mentioned, such as anti-bacterial, anti-phlogistic, diuretic, and anti-depressive, specific clinical applications become more restricted.

In modern European medicine, St. John's wort extracts are included in many over-the-counter and prescription drugs for mild depression, and have clinical application for bed-wetting and nightmares in children. The extract is included in diuretic preparations, and the oil is taken internally by the teaspoon to help heal gastritis, gastric ulcers, and inflammatory conditions of the colon (using a retention enema) (110). The oil is also used extensively in burn and wound remedies, externally.

Table 2, taken from the German Health Department's official monograph on St. John's wort (1984), summarizes the current clinical applications of the plant (105,106).

Herb source: flowers of Hypericum perforatum, "gathered during the time of blooming or of the dried parts above the ground, as well as their preparations, in effective dosages."

Clinical applications: Internally: "psychovegetative disturbances, depressive states, fear and/or nervous disturbances. Oily hypericum preparations during dyspeptic disturbances." Externally: "Oily hypericum preparations for the treatment or after treatment of sharp or abrasive wounds, myalgias (muscular pain) and first degree burns."

Contraindications: "None known." Side effects: "Photosensitization is possible, especially in light skinned people." Interference with other drugs: "None known." Dosage schedule: Average daily dose recommended is 2-4 grams of the powdered herb, or 0.2-1.0 g hypericin as a powdered extract. Method of use: "Cut or powdered plant, liquid and solid forms for oral administration. "Liquid and semi- solid forms for external use." Effects: Mild anti-depressant action (monoamineoxidase [MAO] inhibitor), oily preparations have antiphlogistic activity. "Diuretic activity,...direct effect on smooth musculature."

Toxicity
Besides its long history of use as a medicinal plant, St. John's wort is also known as a photosensitizing plant that can cause sickness and even death in grazing animals (when large amounts are eaten), particularly cattle, sheep, horses, and goats, but also rabbits and rats111. This toxic activity of St. John's wort was first noted in the literature by Cirillo (1787), and since then, there have been many papers published, and the effect mentioned numerous times (112). The plant, however, does not seem to be a major threat to livestock, because the first symptoms of Hypericum intoxication includes loss of appetite, which makes the absorption of the photodynamic pigment, hypericin, self-limiting (113).

In the case of Hypericum toxicity, the compound hypericin is absorbed from the intestine and concentrates near the skin. When the skin of the animal is exposed to sunlight, an allergic reaction takes place. Oxygen is necessary for the photodynamic hemolysis, leading to tissue damage. In the absence of sunlight, a reaction will not occur, and the compound does not show particular toxicity. (114, 115) This first type of reaction is called 'primary photosensitization' (116). Another, more serious type, is secondary photosensitization, where the liver and other internal organs can be damaged (117).