OCD can make us worry about anything, including worrying we’ll catch someone else’s traits. This is often based typically on whatever OCD theme is driving it.
If your child is struggling with contamination OCD they might be thinking they can keep themselves safe as long as they keep track of everything and anything that touches them or the things they care about. This can keep them so distracted and overwhelmed. It is like being on a hamster wheel they cannot get off. But they often think it is worth it, because they are able to control whether they get contaminated.