I have a possible answer to a query posed to you on your website (below as a reminder). The symptoms the gentleman described sound exactly like those I experienced 20 years ago as a young, single soldier living in the barracks. Since I had to do my own laundry, I was very aware of everything I was using. I had started using one of those in-the-dryer fabric softeners when I noticed that I was developing a rash on my face and neck. I had no idea what the cause might be at first, but nothing helped it. It would gradually subside and then reappear a few days later.
I finally went over what, if anything, I was doing differently than I had been and thought about the new laundry product I had started using. I tried to remember whether the changes in the rash coincided with how long I had been sleeping on a particular pillowcase (increased rash with a new pillowcase, gradual remission, then reappearance with a freshly washed pillowcase?), but could not remember. However, on a hunch, I stopped using the in-the-dryer fabric softener, and my rash problem went away.
Coincidence? Possibly, especially since you would think that the clean sheets would also cause a rash on the rest of my body, but did not. However, my facial skin has always been much more sensitive to external agents than the rest of me and to this day I am convinced those handy little sheets were the problem.
I would be willing to bet the inquiring gentlemen made a change in his laundry products; the rashes occur only on his neck and right side of his face because he sleeps predominantly on his right side and they subside over a period of three days as the chemicals lose their potency and/or are rubbed off by use over time. Replacement with clean pillowcases recreates the initial, rash-causing situation.
Just a thought, hope it helps and thanks for a great site!