This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
A solution of citric acid - 60 to 90 gr. in 8 oz. of water - will sometimes markedly relieve the pain of cancerous ulceration. I have verified this fact in cancer of the tongue, of the breast, and of other parts, without being able to explain it. It is not generally known, but has been several times recorded, e.g., by Brandini, by Denny (Lancet, i., 1866), and Barclay (British Medical Journal, i., 1866). Chronic cases of psoriasis and eczema, especially in gouty subjects, are relieved by the daily use of slices of fresh lemon.