Described are compositions and methods for use thereof for prevention or mitigation of allergic reactions in humans and animals. Novel compositions comprised of, e.g., an acidic salt solution of aluminum, calcium or magnesium, are provided for topical or contact application to physically and/or chemically alter an allergenic protein present in the environment and thereby lower the allergenicity of the protein. The compositions of the invention, e.g., comprised of aluminum sulfate, can be used to deactivate many types of proteinaceous allergens such as dust mite and cockroach body dust, animal dander, dried saliva, mold spore antigens, airborne pollen protein and the like. Compositions can be applied on an as needed basis to a wide variety of surfaces, interiors, furniture, pet bedding, plants and the like. The compositions provided may also be utilized to mitigate allergens present on clothing, e.g., for use in commercial dry cleaning or in household laundry applications.