Physical Danger
If you've ever been described as "sharp as a tack," you'll gain new appreciation for the analogy when you drive a sharp tack into your hand instead of the chair you're re-covering. Hurts just to read that, doesn't it?
Take a look at an upholsterer's tools. They can be categorized as "sharp," "sharper," and "the fingertaker." You'll work with a claw-shaped needle strong enough to punch through leather and vinyl. Other tools have fun names like, "ripping chisel," "pincers," and "skewers." This is not for the kid who once accidentally stapled a finger while assembling a book report.
Once you've mastered the art of picking up your tools by the handle and not the pointy end, however, you'll be fine. You might even take on a side job at a Piercing Pagoda and get paid to punch holes in body parts. This isn't a stupendously dangerous job. You work slowly and meticulously, allowing for caution and precision. These are factors that lead to beautiful work rather than bodily harm.