If you want to know if he loves you so It's in his skin

The story:

This song came out in 1963 when I was in Jr High. I liked the song a lot but found it puzzling. I knew nothing of love and so I guessed it was possible that a man's skin could undergo subtle changes when he was in love, and careful attention on the part of the woman to his skin, i.e. temperature, pallor, blotchiness, or moistness, could give her essential information regarding his feelings for her.
At that time, my girlfriend and I would call each other up, synchronize our radios and sing the songs together. It was during one of these sing-alongs that she detected my error. "Skin? Did you say, 'It's in his skin'?" For years after that if we saw a couple holding hands or kissing, she'd say, "Did you notice his skin?"