To the editor:

The simple method of checking vaginal pH discussed by Willyard1 in your “Science on a Shoestring” special report is truly innovative. However, it is important to consider how safe it is to insert into the vagina a pH paper strip made from lichens and treated with toxic chemicals such as cyanidin, phenolphthalein, thymol blue, phenol red, bromothymol blue, bromophenol blue, methyl red, bromocresol green, methyl orange and cresol red (all commonly used in the production of Universal pH paper).

Phenolphthalein, for example, has been banned by the US Food and Drug Administration on account of its tumor- and infertility-inducing potential (ref. 2 and http://ntp.niehs.nih.gov/?objectid=071D1613-04B4-DD88-0B81AC15C02061B8).

The potential hazards of inserting pH paper into the vagina should be given serious thought, and appropriate care should be taken for the safety of patients3. The inability of cotton swabs to collect enough vaginal fluid has been cited as a reason for inserting pH paper strips directly1. This problem could be overcome, however, by mixing the swab contents with a tiny amount of water (pH 7) that can then be smeared onto the pH paper.

The need for cheap alternatives to expensive kits is considerable, but the potential for harm should not be overlooked.