Topical pain-relieving patches — or “shippu”  — are everywhere in Japan. If you’ve ever tweaked your back, strained your shoulder, or felt sore after a long day, chances are someone has handed you one of these cooling or warming patches. They’re available over the counter at any pharmacy, or you might get a stronger version prescribed by your doctor. They’re popular with everyone from office workers to athletes. But do they actually work — or are they just expensive stickers