Boric acid

General information

In the past, boric acid was falsely considered to be relatively non-toxic, and had an unwarranted reputation as a germicide. However, it is only bacteriostatic, even in a saturated aqueous solution, and can cause adverse reactions. Boric acid has often proved poisonous, either by ingestion or after local use. Cases from the world literature have been reviewed [ , ]. In 172 cases of boric acid intoxication, including 83 deaths, 37 deaths occurred after external use, including 23 children with nappy rash. From 1974 to 1984, the Poison Centre in Paris recorded 134 cases of intoxication with boric acid or borates, 88 of which were accidental and 31 iatrogenic.

Boric acid was first used as a topical antiseptic by Lister in 1873. It has subsequently been used in eye washes, mouth washes, skin powders, and ointments. Boric acid has also been as an irrigant for body cavities, including the pleural space, vagina, and rectum. The medical use of these solutions and irrigants has now been abandoned, because of toxicity and potential lethality. However, boric acid is used as a household disinfectant, and deaths due to accidental poisoning are still reported [ ].

Boric acid penetrates even intact skin, but it is readily absorbed through inflamed or otherwise damaged skin and through mucous membranes. After the application of wet compresses of boric acid to intact and eczematous skin in 21 patients over several days, blood concentrations of boric acid were generally not raised [ ]. One patient, however, did have a significant rise in blood boric acid concentration, which the authors ascribed to pre-existing kidney insufficiency.

Prolonged absorption of boric acid causes anorexia, weight loss, vomiting, mild diarrhea, skin rash, diffuse alopecia, convulsions, and anemia.

Because of toxicity and the limited therapeutic value of boric acid, the borates have been abandoned as obsolete in many countries.

Drug studies