Hands go through a lot that the rest of the body doesn't, constant washing, hand sanitiser, dishwashing, cleaning products, gloves that trap sweat. That makes hand eczema its own thing to track, with its own set of everyday causes worth noticing separately from the rest of your skin.
It's easy to lump "my skin" together as one general thing, but hands are exposed to a completely different set of triggers than, say, the back of your knees. Marking hands specifically, and noting what your hands actually did that day, helps separate hand-specific causes from everything else.
Small swaps, like switching to a gentler soap, wearing gloves for washing up, or moisturising straight after every wash, are easy to try but hard to judge from memory alone. Logging hands specifically for a couple of weeks makes it much clearer whether a change is actually helping, rather than just hoping it is.
This is general, practical information, not a diagnosis or treatment recommendation. Hand eczema that's cracked, bleeding, or not settling is worth showing a doctor or dermatologist.
This is exactly what I built SkinFam for, a private, on-device diary with a body map you can mark hands (and feet) on specifically, alongside notes on what they were exposed to that day. Nothing you log ever leaves your phone. Get SkinFam free on the App Store.