Disclosed are treatment compositions comprising a liquid emulsifiable concentrate which comprises a chemically unstable reactive agent wherein the reactive agent is comprised of one or more reactive groups of the electrophilic, nucleophilic or protected thiol type, a water immiscible solvent, one or more surfactants, which is usable upon dilution within a separate aqueous composition to form a micro- or macro-emulsion in-situ immediately prior or simultaneous to application to the substrate and wherein the reactive agent is chemically shelf stable. Also disclosed are methods for treating amino acid based substrates, and methods for bleaching, coloring and conditioning hair with these treatment compositions.