Allergic???

Hey ladies, just curious-- my husband was just stung by a bee, he's never been stung by one before & neither have I. I googled symptoms and all but still not sure because the swelling looks pretty bad (to me) and is warm to touch and painful. I don't think he's allergic, although his mother is and has an epi pen, I'm just wondering... does this look like it could progress..? Like more swelling?? Into an allergic reaction?? I'd like to save a couple hundred dollars trip to the ER if this is normal. Please let me know. Thank you.