Paranoia About Wife's Estrogen Cream Transfer

My wife is 53 and uses estrogen cream to combat menopausal hot flashes. How long after application should I stop being concerned about the transfer of said estrogen from her skin to mine?

1. About 15 minutes after she applies it?
2. Some number of hours post-application?
3. The next morning?
4. Not until after she showers or washes it off?

She seems to believe #1 is the right answer, claiming that it is rapidly absorbed and not a threat after that. However my paranoia prevails.

My question has largely to do with morning sex. She puts the stuff alternately on the back of her knees and on her forearms, either of which I will definitely come in contact with during a normal roll in the hay.