Chicken pox

I as a caregiver would not be going near anyone that has or has been in direct contact with a contagious sickness, that my child is not vaxed for/could get. So you have to pose it to him like that.

If his friend did not have chicken pox before, then no, it's not a good idea.

I think it’s highly unlikely…

Have the adults had pox before? You could come into contact with many adults carrying things from their children in all walks of life. I think it’s still ok for him to go

The adults can definitely carry it without being ill, but like the above said they could really get it from anywhere and if you thought like that you’d never be able to leave the house! My little boy got chickenpox about 6 weeks ago, no one we knew had it recently, he could have picked it up from anyone.

If it makes you feel any better my 2 year old got it and passed it onto my 8 week old which I was really scared of but both were fine! Weren’t phased by it, only had a few spots that didn’t seem to irritate them and got over it quickly!

If the adults have both had chicken pox it's highly unlikely that anything would be transmitted to your 4 month old this way. In an abundance of caution maybe your partner could ask his friend to shower and change into fresh clothes before leaving the house?