Just to stay on the same page with everyone... there's some evidence that Judy's reaction has nothing to do with salt water. She's been in other salt water pools, and the ocean, without reactions. The current hypothesis is that there was some additive or foreign material in one of the salt bags that is causing the problem. Tracking the salt level as she replaces water is a relatively logical way to track the dilution process, but if this resolves her problem, it's not logical to assume it was the lower salt level that solved it. It will more likely be the dilution of the foreign compound, the identity of which has yet to be determined.
Also keep in mind, that should she be successful in diluting out what was causing her symptoms, that will resolve the current issue, but she'll never have found out what the actual culprit was, and so she won't be able to avoid it happening again... The dilution process is flushing out the evidence as we speak.
The ultimate solution would be to have the water chemically analyzed, and then allow her dermatologist to do scratch tests with any suspect chemicals discovered, and then really understand what caused Judy's allergic reaction. I don't know if that's practical or not. Just throwin' it out there...
By the way, date-wise, where is the addition of the water filter system relative to the appearance of the symptoms? Any possible correlation there?
It took months to flush out some sort of manufacturing compound from my new RO water filter. I should have taken it back. I think it was some kind of oil. It's clear now, but my RO water was not healthy for a while there...