I sent the email with the picture from the previous post to my dermatologist last Sunday, called on Tuesday, and finally got hold of her on Friday. So it had been almost two weeks since I started the "Efudex experiment," and I wanted some professional advice. The area on my scalp continued to have only a mild reaction, which makes sense if the previous Efudex treatment had removed most of the sun-damaged cells. But the area on my left cheek had continued its strong reaction, and was burning to the extent that I had started to apply vaseline over it to ease the burning.
I was a little surprised by what she said. Apparently she had just returned from a conference at which she had discussed my experiment with a few of her colleagues. And whereas at our last appointment she had agreed that reapplying Efudex to an area that had recently been treated should not yield a significant reaction, her colleagues had convinced her that it would probably react even if the previous treatment had been effective. Well this makes no sense to me. In the original treatment, some areas reacted, presumably because those areas contained rapidly-dividing, sun-damaged cells. And other "normal" areas didn't react. So if the previous Efudex treatment really removed most of the rapidly-dividing, sun-damaged cells the treated skin should now be "normal" and there shouldn't be a strong reaction to a subsequent efudex treatment. Right? But she said that nobody has ever done such an experiment! Why not? Because 1) most people don't like to use the Efudex again, 2) if the skin looks smoother after the Efudex treatment, it must have worked, and 3) the condition is not life threatening anyway.
So she didn't see any point in continuing the Efudex on my cheek. It was previously treated for two weeks to the point that it turned red, it looks smooth on the outside, so it's fine. And even if it's not fine, it wouldn't be life-threatening anyway. On the other hand, I think that the strong reaction this time must indicate that there is still significant sun damage and that I might as well treat it for a while longer to try to remove that sun damage. She warned me not to go too long since it could become a mess and get infected, and we said goodbye.
So it appears that I am on my own for the rest of this experiment. I've stopped applying Efudex to the area on my scalp, since that area did not react. But I will continue for a while longer on my cheek. But perhaps not too much longer since it has already reacted more than the first time, with a few spots starting to ooze. Perhaps one more week? We'll see how it progresses.