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.
Tag Alder, Black Alder, Alnus serrulata. Not official. The bark and leaves contain tannin, oils, and a resin. Just what constitutes a drug a "vegetable alterative," or what such a drug really does, I confess I don't know; but I do know, from abundant clinical experience, that alnus is such a drug and that it clears up a "pimply" skin and a tendency to a "crop of boils" in a highly satisfactory manner. What used to be called "scrofula" that was not tubercular (lymphatism?) is the indication for this drug. Fl. in 15- to 20-minim doses.