Okay. You can give diphenhydramine HCl (in the USA, that is Benadryl, but in the UK I think Benadryl is something else, so ask your chemist for diphenhydramine HCl. You would want to give 1mg/lb about an hour before people are going to be coming over.
For a more natural solution, you can also try a DAP collar:
It is a pheromone collar that is calming and soothing, and that is very natural. You would put it on him a half hour before people come over.
You can try Composure Liquid, which is natural:
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