Ichthyol is an aqueous solution of the ammonium salts of sulphonic acids prepared from the distillate from bituminous shales found in the Tyrol and elsewhere. These shales contain the fossil remains of fishes.

Properties : Ichthyol is a reddish brown to brown-black syrupy liquid having a characteristic empyreumatic odor and burning taste. It is miscible in all proportions with water, glycerol or oils, but is incompletely soluble in alcohol. Its aqueous solution has a faintly acid reaction.

Action and Uses: The actions of ichthyol are not well understood. It penetrates the unbroken skin to a certain extent. It is said to act as a vasoconstrictor on mucous surfaces. It has a mildly antiseptic action. On account of its content of sulphur it is credited with alterative properties.

It is applied to the skin in inflammatory conditions such as erysipelas, acne vulgaris, rosacea, lupus erythematosus, etc., to lessen hyperemia. It has also been used internally, but it is impossible at present to determine its true value. It has no specific action in tuberculosis, although it has seemed to increase appetite and strength in some cases. It has been tried with some apparent success in angioneurotic edema. It is used as a local remedy in gynecologic affections to relieve hyperemia and pain.

Dosage: The application of pure ichthyol to the skin is somewhat irritating, but a solution of 25 per cent, strength is generally not irritating. In chronic rheumatism a 50 per cent, ointment has been used locally. In gynecology it is combined with glycerol 1:10. Internally it may be given in solution or in the form of pills. The dose is from 0.2 to 2 c.c. or from 3 to 30 minims.