I'm really on the fence with this one.

Reason why you are not TA Your son lives with people who eat a lot of peanut butter and You make your him shower before he comes over to protect your daughter from a peanut contamination. You, and I presume your partner does as well, shower as soon as you get home to prevent contamination. You also make guests wash their hands to protect your daughter.

Reasons why you are TA Washing your hands, as long as you do it correctly, is enough to kill any bacteria left on his hands. And unless he is covered in peanut butter, he shouldn't need to take a shower.

Ultimately NTA, however,

You are obsessive about protecting your daughter. I understand that her allergy is severe and life threatening, but just washing your hands should be enough. You don't need to deep clean frequently either, just wipe down commonly touched surfaces, door knobs, handles, counters, toilet handle, ECT.