What Causes Red Bumps In The Waistline?

My wife and I both are ocassionally experiencing red bumps exclusively around our beltline. We are thinking it could be from an insect, but it is winter! Could we have bed bugs in our furniture? If they were in our bed wouldn't the apparent bites be in other locations too? We have two cats, but they are treated with flea/tick medication each month and we have not seen any insects anywhere. Could there be another explanation?