Studies show one in three shower heads are contaminated with mycobacteria, a hardy strain of bleach-resistant germs that can penetrate lung tissue, causing fatigue, weakness and shortness of breath. What's so bad about showerheads? “They are dark, wet and warm, an ideal environment for the growth of these bugs,” explains Michael Schmidt, Ph.D., professor of microbiology at Charleston’s Medical University of South Carolina. “Plus every time you scrub your hair, you splash protein-rich shampoo (a mycobacteria fertilizer) up into the shower head to further boost the growth of these bugs.” Fortuantely, switching to baths can prevent their inhalation, say University of Colorado researchers. Not into tub time? Scientists say scrubbing your shower head weekly with a bit of water and a firm-bristled brush can also cut bacteria levels in half.