@andyd Thanks for the reminder not that it was your intention.
I have leather bags (from Time Resistance, hand made, Florence, highly recommend), a backpack and a sling bag (such a primal, ancient shape, like a bag for holding seeds in the field- my favorite) AND the leather requires a certain type of balm.
You can buy it from the company or elsewhere. I've decided I will buy it from the company.
I'm remiss for not doing it already.
The other day I saw my backpack in the sunlight.
I wiped it down with a solution of light vinegar and water. Then I dried it immediately.