A tissue treatment system comprising: a base unit having a power source and a reservoir for containing a cooling fluid, an applicator connected with the base unit via a cable, the applicator comprising: a tissue cooling element constructed and arranged to engage biological tissue for treatment, the tissue cooling element including channel structure (58, 60) there-through, a light source powered by the power source and constructed and arranged to generate light energy directed to the tissue cooling element and thus to the biological tissue, a first fluid passage disposed between the reservoir and the channel structure (58, 60) of the tissue cooling element and configured to deliver cooling fluid at a first temperature to the tissue cooling element to cool the biological tissue, such that the cooling fluid is heated to a second temperature upon heat exchange with the biological tissue, and a second fluid passage disposed between the channel structure (58, 60) and the reservoir and configured to return the cooling fluid to the reservoir, the second fluid passage being constructed and arranged to direct the cooling fluid, at the second temperature, to the light source to cool the light source prior to being returned to the reservoir, wherein the first and second fluid passages define a single cooling fluid circulation loop to cool both the tissue cooling element and the light source in series, and wherein a portion of each of the first and second fluid passages is disposed in the cable. a base unit having a power source and a reservoir for containing a cooling fluid, an applicator connected with the base unit via a cable, the applicator comprising: a tissue cooling element constructed and arranged to engage biological tissue for treatment, the tissue cooling element including channel structure (58, 60) there-through, a light source powered by the power source and constructed and arranged to generate light energy directed to the tissue cooling element and thus to the biological tissue, a tissue cooling element constructed and arranged to engage biological tissue for treatment, the tissue cooling element including channel structure (58, 60) there-through, a light source powered by the power source and constructed and arranged to generate light energy directed to the tissue cooling element and thus to the biological tissue, a first fluid passage disposed between the reservoir and the channel structure (58, 60) of the tissue cooling element and configured to deliver cooling fluid at a first temperature to the tissue cooling element to cool the biological tissue, such that the cooling fluid is heated to a second temperature upon heat exchange with the biological tissue, and a second fluid passage disposed between the channel structure (58, 60) and the reservoir and configured to return the cooling fluid to the reservoir, the second fluid passage being constructed and arranged to direct the cooling fluid, at the second temperature, to the light source to cool the light source prior to being returned to the reservoir, wherein the first and second fluid passages define a single cooling fluid circulation loop to cool both the tissue cooling element and the light source in series, and wherein a portion of each of the first and second fluid passages is disposed in the cable.