This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
Pyrogallol. Pyrogallol. - C6H3(OH)3,=125.7. Synonym. - Pyrogallic Acid.
Light white, shining laminae, or fine needles, odorless, and having a bitter taste; acquiring a gray or darker tint on exposure to air and light.
It is used externally as an ointment (Jarisch's ointment is pyrogallic acid, 1; lard, 8) for the treatment of chronic psoriasis. It is also an excellent parasiticide for ringworm. Before pyrogallol is used, vaseline should be applied thoroughly, and wiped off, to remove scales and other morbid products. It must not be applied over too large a surface, as it may be absorbed, and then it breaks up the blood corpuscles, causing methaemoglobinuria and Jaundice. Jarisch's ointment is very strong; a more usual strength is 1 or 2 or even less to 48 of lard. When it is applied in solution or ointment, it stains the skin, but not permanently; linen and clothing are, however, permanently darkened. To avoid the staining it has been proposed to dissolve the remedy in flexible collodion, 1 or 2 to 24.