Skinvincible

When Spider-man got his cosmic powers, Magneto came to check him out in case he was a mutant. That's when I learned that some mutants don't show their powers when they're born, but develop them later in life. I assumed that's the way it was with my super power.
I'm a fair-skinned guy, and it's not surprising that I'm sensitive to the sun, and I'd been burnt pretty good when I was a kid. About a year ago, though, I spent a week with my brother in Las Vegas during the summer. It's different going to Vegas with my brother, because we didn't do any of the touristy things. We just hung out by the pool all day every day, and then went to the casinos at night. Even though I laid by the pool without any sunscreen for about four hours every day, I didn't get burned or tanned or anything. It was as if the sun had no effect on me whatsoever. I was skinvincible.
I don't know how long I've had this power, but that was the first time I'd seen it in effect, but now I can't remember being really sunburned since high school when we'd go boating. This week, however, I discovered that my power wasn't a mutant evolution after all, but from a different source.
On Monday I spent a large chunk of the day outside in the sun at the Braves game. The newly-exposed skin on my head got burned bad. Maybe the worst burn that I've ever had in my life. Yesterday it blistered up. Last night the blisters burst. This morning my head is swollen all around the burn on one side. I look like I had some birth defect that makes my head lop-sided.
Now some might say that my skinvincibility was just a joke or my imagination, or that I simply don't get enough sun to test it since I'm just a indoor-dwelling computer guy. I insist that my powers were real, and it's obvious to me what has happened. I simply lost my power when I shaved my head. Every super-hero has a weakness. I guess the haircut was mine.