This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
Juniperus communis. The berries are official except in Great Britain and the U. S., but Oil of Juniper is official in both of these countries.
Juniper is a diuretic which acts by a slight irritant and stimulating influence on the renal epithelium. Diuretics of this class are losing in professional favor, the preference being given to those acting indirectly. Pharmacologically, the action is akin to that of turpentine.
Juniper is an efficient but irritating agent used in the treatment of dropsies of various types, but not when nephritis is present.
The oil is given in 3-minim doses, the spirit in 30-minim doses, and the compound spirit in 2 fluidrachm doses.
Oil of Cade, from Juniperus oxycedrus, is nearly universally official. It is also called Juniper Tar Oil. Externally the action is that of tar, but it is less objectionable in use. It is employed in chronic forms of eczema, psoriasis, lichen, prurigo, etc., and as a parasiticide in favus and tinea. Oil of cade is used from weak, oily solutions up to full strength.
"Haarlem Oil," a popular remedy in lay circles, is said to be composed of equal parts of oil of cade and oil of juniper berries.