Any ideas for this?

I first noticed my husband was getting alot of what we thought were brown recluse spider bites. The reason I'm not thinking they're spider bites anymore is because he gets around 3-4 of these "bites" a year. I don't understand why this would  be happening to him and not me, since we both sleep in the same bed/areas.  However, they look like the brown recluse bite. Black, dead skin (in the shape of a circle) surrounded by reddened skin, to about the size of a quarter, sometimes larger. What on earth could this be, other than a spider bite??