DeSantis makes the majority of our holsters, and this statement is from them:
"Do not apply leather dressings, mink oil or mitt and glove dressing to your holster.  These will soften the leather to the point it loses retention properties.  'Massaging' or kneading a leather holster may also soften it to the point where retention qualities are lost.  This practice should also be avoided."We can only recommend using a little bit of saddle soap if you need to clean your holster.  Otherwise, leave it be or risk losing the retention properties.