I've just been doing some research lol, and white areas on your nails seem to be generally regarded as being caused by stress or a zinc deficiency. Have a chat to a chemist re adding a zinc supplement into your meds, but it's got to be worth a try - its very common apparently....

Quoted from Fitday site...
"Eating a diet rich in zinc foods is a necessary part of maintaining your dietary health. Zinc contributes to many aspects of your general health. It contributes to quality of eyesight, taste, smell, hair and skin. It is also linked to the production of testosterone in men and the lessening of PMS symptoms in women. It even boosts the health of pre-natal babies as a necessary component of healthy birth weight.
But, perhaps the most widely known benefits of proper zinc intake is a fortified immune system. Zinc aids in the building of 100 different enzymes, and helps protect the body against sickness and decay."

That seems to prod some very interesting buttons....immune system (yep that's crap with CRPS), various benefits to skin (which of course is the focus for so much of the symptoms). Might add a supplement of it myself!!!

Foods with good zinc content include:
Meat, shellfish, nuts and seeds, milk, cheese, bread, cereal (those last two are no good for me, being a coeliac!).

Hope this helps a bit, and thanks for prompting me to research it. Sounds like its worth adding something into my own diet. I'm going to add vitamin C and zinc now, maybe even a general supplement. I'll talk to my chemist!

Bram.