pH factor of TMA and normal skin pH

The University of Washington, Seattle, funded by the National Institute of Health, published an extensive article on Trimethylaminuria [Fish Odor Syndrome, TMAuria, TMAU] in which they list "best-practice" guidelines for the treatment of this disease. Included in these guidelines are use of acid soaps and body lotions,

Trimethylamine is a strong base (pKa 9.8). Thus, at pH 6.0, less than 0.02% of trimethylamine exists as the volatile free base. The use of soaps and body lotions with a pH close to that of normal skin (pH 5.5-6.5) helps retain secreted trimethylamine in a less volatile salt form that can be removed by washing.

full article: Trimethylaminuria. National Center for Biotechnology Information (NCBI) U.S. National Library of Medicine, U.S. National Institutes of Health (NIH)