Asynchronous challenges

We're getting to the tail end of the discovery stage of our diet to find the cause of my son's eczema.  Last week my son challenged bread preservative (three crumpets a day, whether he liked it or not; he liked it) and I challenged salicylates again.  We'll do a glutamate challenge later this week, and then we have the option of challenging additives, challenging salicylates again (this would be my son only, as I have just done this), or starting the salicylate reintroduction.

Normally you don't repeat a challenge unless you have reason to believe the results will be different.  I challenged salicylates a second time because we suspected that my mood from the first challenge may have been due to other factors, including the condition of my son's skin during the challenge and anxiety about the results.  In contrast to my first salicylate challenge, which was done at the same time as my son was challenging salicylates and was our first challenge, this last week I experienced no listlessness or irritability, nor did I have any digestive discomfort, so I have concluded that I do not have a sensitivity to salicylates.

The argument for repeating the salicylate challenge with my son is that the results the first time were inconclusive; his skin, though possibly better than it had been prior to the start of the diet, was never clear of eczema, and the dermatologist pointed out that skin irritation that is already present will change intensity without provocation.  We've also discovered recently that even when we clear all signs of eczema by applying cortisone and strictly follow the diet, it takes only three days for some irritation to reappear, so there is some background noise, making it difficult to ascertain the results of any challenge ('his skin got worse, but how much of that was due to the food versus what would have happened anyway').  We observed this pattern during the recent bread preservative challenge, when his skin slowly got worse throughout the challenge until we used cortisone at the end to clear his skin for the next challenge.  The big question is: how much worse?

Perhaps the diet isn't working at all for him.  Have I deluded myself into believing that his skin improved?  Right from the start I struggled to find a way to codify the condition of his skin.  With each new food diary (we're on our third) I have tried to clarify the meaning of the 0-5 scale that I ended up using.  In retrospect, there has been much more value in the notes I've kept describing the locations and extent of the irritation than in the numbered scale the dietitian recommended, but I didn't work that out until I was into the second notebook and starting the challenges.  Realistically, he needs to do the elimination diet for 13 days after clearing his skin with cortisone to find out what happens so we can use the results to filter the results of the longest challenge (salicylates: three days of elimination prior to starting, seven days of salicylates, and three days of elimination following).  But honestly, after three months of this I don't know how much more of it I can stand.

We can skip the second salicylate challenge, assume that my son is moderately sensitive to salicylates based on the results of the first challenge, and start the reintroduction.  To reintroduce salicylates, you eat a very small amount of a food that contains low levels of salicylates once every few days.  After two weeks, if your symptoms have not worsened, then you increase the amount or frequency.  You continue this until your symptoms worsen, then back off to the last level and maintain that (or less).  But since my son's skin will worsen on its own, without the contribution of salicylates, this process would have us conclude that he can withstand no amount of salicylates.

So my conclusion is that we will both challenge glutamates this week, which requires eating soy sauce and parmasean cheese, then my son will challenge salicylates again.  Hopefully we will either see a clearer signal or no sign at all (preferably the latter).  We'll continue to avoid additives, but following the final challenges we will not be remotely as fastidious about what we eat.