Ri. Murahata et Mp. Aronson, THE RELATIONSHIP BETWEEN SOLUTION PH AND CLINICAL IRRITANCY FOR CARBOXYLIC ACID-BASED PERSONAL WASHING PRODUCTS, Journal of the Society of Cosmetic Chemists, 45(5), 1994, pp. 239-246
The influence of formulation pH on the irritation potential of slurrie
s formed from two commercial products composed entirely or partially o
f aliphatic carboxylic acid-based surfactants (fatty acids and their s
alts) was determined in vivo by use of a flex wash. Increasing the pH
of a synthetic detergent/fatty acid slurry from its neutral value to a
pH of 10 reduced its mildness. The neutral pH of the predominantly no
n-soap-based cleanser, therefore, makes a significant contribution to
its mildness. If it were formulated at pH 10, it would be significantl
y harsher to the skin than the current neutral formulation. The pH als
o had a significant effect on the irritation potential of soap-based c
leansers. Decreasing the pH of soap slurries from their ''normal'' pH
of approximately 10 to pH 7 reduced their irritation potential. The di
fference in alkalinity, as measured by pH, is directly related to the
lower irritation potential of both of these formulations. These result
s demonstrate that pH has an important role in determining the differe
nces in irritation potential of these complex skin cleansing compositi
ons through effects on ionizable constituents.