With a long, dense coat that traps dirt and oils, Shih Tzus require regular bathing every 3 to 4 weeks. The more hair-like texture of their coat can make it prone to matting, which should be brushed out before bathing to prevent tightening. In addition to regular bathing, it is recommended to take Shih Tzus for professional grooming every six to eight weeks to get a trim and maintain their coat. Find the right dog shampoo for your Shih Tzu at Lillian Ruff.