Almost my entire family is itchy/bumps. Read all?

Okay, so for about 5-7 days or so my mom and I have been getting itchy bumps randomly on our bodies. They re small and red (like a pimple with no head), itchy, and are grouped on certain parts of our bodies. My mom has them on one of her arms and I have them on my right hip. There s also a few on my leg and a few on her back. My dad has also gotten these bumps on his legs and back as well as my grandmother.
The thing is, we don t think it could be bed bugs or fleas because #1, my baby brother (3) sleeps in the same bed as my mom and has not had any bumps. #2 we have a dog and two cats and they haven t been behaving as if they have ticks or fleas.
We haven t started using new detergent or soaps, and all of us sleep in seperate rooms.
What could this be?? Please help.