A computer-implemented method can include receiving a first image input from a user, determining values of biological properties of the user, determining a first formulation, controlling a plurality of servomotors, receiving a second image input from a user, determining a second value of one of the biological properties of the user, comparing the first and second values, changing another of the values, determining a second formulation, and again controlling the plurality of servomotors. The image inputs can include images of the user's skin. The values can be representative of a sensitivity of the user's skin to one or more materials and a current level of irritation of the user's skin. The formulations can contain a plurality of materials and can be configured to inhibit irritation of the user's skin based on the values of the biological properties of the skin.