I get blisters under my feet when wearing trainers so I now always use proper 3 season leathe boots which also help against plantar fasciitis
If I expect a blister for any reaon I put vaseline on the area as blisters are caused by friction.
I also use liner socks, despite boot sellers saying only one pair of socks, as liners socks reduce friction
Before I knew how to prevent blisters I sometimes had burst bleeding muddy blisters which always healed
But one blister, from doing 3 peaks in trainers, I pierced with a sterilised needle. It went septic and I needed pencillin!

I wondered if the collective LDWA wisdom can help with this one?

I completed the Bullock Smithy on Saturday (and Sunday morning...!) and suffered with large very painful blisters on the ball of my foot behind my big, second & third toes. I have completed a number of events of this sort of distance before and had the odd heel blister in the past but never suffered like this. My friend also had the same problem.

Does anyone have any idea what could have caused this and any suggestions for avoiding the problem in the future