How to treat and prevent bed bugs

My stepson keeps coming back from his moms and within 24 hrs he breaks out, with suspected bed bugs. He never breaks out again. I’m wondering if they aren’t still on him and then as soon as we shower him they disappear until the next time he comes back. I’m going to start showering him right away when he comes home but I want opinions on how to clean his mattress and prevent them. I hate hate hate that this is the case. I have never had them and am completely clueless. Our house stays very clean and doesn’t have clutter.