Husband licking the clitoris of the wife

It is unadvisable to lick this area. Further, this area could be covered with impurities. It is likely that in the heat of excitement, some impurity is swallowed and obviously swallowing an impurity is haraam. Everything that is pure does not have to be licked. For example, the filth from the nose, even though it is not najis (impure), definitely it is very filthy to lick it. Similar is the position here; whilst it may not be totally haraam, definitely it is extremely filthy and disgusting.