Once my back, ass, and breasts are warmed up and showing some nice welts my husband often will request the master or mistress to aim directly for my under arms as they welt up more severely than my back. It obviously adds to my reaction making for the excitement of anyone invited to witness my whipping including my husband and the man or woman administering my flogging.
The whipping of the two partners (wife and husband as well) is not at all a "punition" but rather a real fun natural exercice where both are really concerned by the mutual ENJOYMENT. That's the same for frictions with stinging NETTLES we regularly practised in public with my lovely 3rd wife : her superb small nipples and her largely opened vagina endured naturally the stinging as well as my genitals I always offered, in holding up position, spreading my thighs.
Another erotic whipping my husband and I enjoy watching during sex or while whipping each other. Really enjoy seeing the welts appear all over her beautiful well stretched out body. He was letting his whip strikes at her breasts wrap around her body leaving nice marks under her arms as well as her breasts, stomach and pussy. I really enjoy the bite of the whip under my arms as well as the rest of my body.