This morning, I spent a fair amount of time clearing out excess growth of
tomatoes in my little greenhouse. When I washed my hands, they turned very
yellow. That had happened before but I did not know what the cause was. I
thought that I had contacted nitrates from my nutrient solution and that it
had somehow caused the yellow color the same way that exposure to nitrate
does. I presumed that the alkaline soap was the proximate cause for turning
a leuco compound yellow.

This time, after washing away the color, I went back out and handled the
tomato plants some more. Hand washing brought out the yellow color again.

Is this typical of tomatoes? What is the substance involved?

Bill