To the Editor : For several years I have been interested in the hydrogen ion concentration in saliva and I have, in my limited way, collected some knowledge regarding it which I believe should be disseminated. Many patients with perleche and some with cheilitis, glossitis, and stomatitis, having failed to respond to routine therapy such as hygiene, vitamins and minerals, malocclusion corrections, etc., are found to have a strongly acid salivary reaction. The salivary pH of the first patient whom I studied was 4.9. Systemic and local alkalinization solved the problem. pH determinations are of much value in pruritus and in "painful skins" associated with sodium and potassium imbalances and salt retention. The dental literature contains some helpful information on the pH of "normal" saliva. The determination, to be of value, must be very carefully done. The sample of saliva should be tested immediately after it comes from the mouth and