A device comprising: one or more emitters configured for application of a stimulus to a skin surface of a subject; a voltage or current supply adapted to generate a waveform for application of the stimulus to the skin surface of the subject, via the one or more emitters; and a controller configured for modulating a set of consecutive pulses in the waveform, wherein the set of consecutive pulses defines a treatment cycle having one or more phases, each of the phases defining a continuous subset of the consecutive pulses; wherein pulse widths or absolute integrated amplitudes of the consecutive pulses vary over at least one continuous subset defining at least one of the phases, or over the set of consecutive pulses defining the treatment cycle; characterized in that the one or more emitters comprise at least one electrode disposed adjacent the skin surface; wherein the waveform comprises an electrical waveform adapted for application of the stimulus to the skin surface as a microcurrent treatment, emitted via the at least one electrode; wherein the pulse widths or absolute integrated amplitudes of the consecutive pulses vary in a predefined, randomized or pseudorandom sequence, such that the pulse widths or absolute integrated amplitudes are non-repeating or aperiodic over one or more of the phases, or over the set of consecutive pulses defining the treatment cycle; and wherein the sequence is constrained to provide a same duty cycle over each phase of two or more of the phases, or to provide charge balance over two or more of the phases having consecutive pulses with opposite polarity. one or more emitters configured for application of a stimulus to a skin surface of a subject; a voltage or current supply adapted to generate a waveform for application of the stimulus to the skin surface of the subject, via the one or more emitters; and a controller configured for modulating a set of consecutive pulses in the waveform, wherein the set of consecutive pulses defines a treatment cycle having one or more phases, each of the phases defining a continuous subset of the consecutive pulses; wherein pulse widths or absolute integrated amplitudes of the consecutive pulses vary over at least one continuous subset defining at least one of the phases, or over the set of consecutive pulses defining the treatment cycle; characterized in that the one or more emitters comprise at least one electrode disposed adjacent the skin surface; wherein the waveform comprises an electrical waveform adapted for application of the stimulus to the skin surface as a microcurrent treatment, emitted via the at least one electrode; wherein the pulse widths or absolute integrated amplitudes of the consecutive pulses vary in a predefined, randomized or pseudorandom sequence, such that the pulse widths or absolute integrated amplitudes are non-repeating or aperiodic over one or more of the phases, or over the set of consecutive pulses defining the treatment cycle; and wherein the sequence is constrained to provide a same duty cycle over each phase of two or more of the phases, or to provide charge balance over two or more of the phases having consecutive pulses with opposite polarity.