Here's the ultimate answer: dermatologists use (and have used for years) "bleach baths" (Google for it!) to treat a variety of skin problems in both adult and PEDIATRIC patients. The "bleach bath" protocol involves whole body immersion in lukewarm water with 50 - 100 ppm chlorine (from bleach) and ZERO stabilizer.

Now, I'm not recommending 50 ppm FC even for your friend with CYA=250 . . . but not because it's dangerous; he just doesn't need it!

And FC=50ppm + CYA=0ppm *will* damage swimwear. It might damage swimwear with CYA=250, though the evidence seems to be against it.

But FC=10 ppm with CYA=250 ppm is NOT a risk for your friends kids.