If it's hanging out on your deck, look for piles of wooddust and/or small holes on the underside of rafters. It's probably a wood bee.

There is no such thing as a bee that is less than useful. Your bee is some sort of native bumble bee. They are actually more efficient pollinators than honey bees, so even more useful. Also, they are often solitary bees which means they don't have a hive to protect, so are very unlikely to sting. Much less so than even honey bees. Hopefully that is reassuring to you and your friend. Bee sting allergy is something I do not envy.

Martha

Thank you! I was just worried about hive activity, as he kept returning every day to the same lookout spot on my deck railing. We will leave him bee!