185. Why aren't you supposed to touch halogen bulbs with your bare hands?
When they're operating, halogen bulbs become extremely hot, so you certainly wouldn't want to touch them then. But even when a bulb is cool, touching it would deposit greases and salts from your skin onto its surface. The aluminosilicate glass used in the lamp's envelope would be weakened when these salts are baked into the glass during the lamp's operation and the greases would scorch and darken the bulb's surface.