Catnip armpits?

My brother was just over on a visit and the six month old little girl really loved his right armpit, she'd stick her head in and snuggle against it and get really purry. She also rolled in his shirt when he left it on the floor. He says nearly every cat he meets has the same reaction and I witnessed it myself in his mother in law's cat last year. They only ever do it on the right armpit, not the left. Strange!

Probably reminds her of snuggling into her Mom's belly.

More sweat glands on the right side?

I have noticed this kind of behaviour with one of my cats, with certain males we know who aren't the cleanest of people (to put it politely!) They must love the smell!!!