The present invention relates to novel compositions of matter and their use in medicine, in agricultural applications, and in cosmetics. The compositions are based on a thixotropic aluminum hydroxide chloride which has an atomic ratio of aluminum to chlorine of from 5:1 to 6:1, and which is the chlorination product of pseudoboehmite which aluminum hydroxide chloride is in a concentration in water of from about 2 to about 20 weight percent. For medical topical application a suitable carrier is impregnated with such thixotropic microcrystalline aluminum hydroxide chloride.