Semen detection kits can be used to detect semen on underwear or clothing. While a UV light will make semen fluoresce, the underwear itself will also fluoresce due to the nature of brightening agents in most commercial detergents. So, a UV light (with yellow glasses) will not be sufficient.
However, moving to a longer royal blue wavelength (with orange barrier glasses) will fluoresce organic material like semen with good contrast and allow it to be visualized.
If you want to check underwear for semen, consider our XeLED-Cr1BL-R6-455-K crime scene kit. If on a budget, the XeLED-Cr1BL-R6-470-K may also work in most cases.