La sal no se adhiere a un dedo seco

[Glen]

I still can't get my head around this one. Sure, "salt won't stick to a dry finger" but how can I apply it figuratively?

[JPablo]

El que se pica: ajos come.

Moliner gives us,

quien se pica ajos come Refrán con que se expresa que alguien que se resiente por una cosa que se dice en general debe de tener motivos para creerse aludido. 1 El que se pica ajos come.

So, if you are "clean", nothing can affect you...

If you have something to be "affected" (water, high level of humidity), the salt is going to "stick" to your finger.

I take you can take it in the negative way or the positive way. (I gave you the negative side, more or less).