Hi David
Good to see you back - sorry I didn't get back to this thread sooner - been away a few days.
Sorry to report that the antibiotic you're on; Cephalexin, is included among those known to cause neuropathy. It's in a class of antibiotics called Cephalosporins. Here's a link to an article which specifically mentions them. (scroll down to you find the section on Cephalosporins)
Neurotoxic effects associated with antibiotic use: management considerations
I sincerely hope you don't have any further reactions and increased PN symptoms. I know you've dealt with these before but it still sucks. The only slightly positive news I can give you is that I had (undiagnosed) PN when I was given Metrondiazole (Flagyl). My PN went from feet and hands to intense full-body. While I still have full-body PN the intensity/frequency has slightly reduced - although summer and heat still ramps it up.
All the best - let us know how you're doing.