Wow, you ladies are awesome. Thanks to all of you for responding. I'm lumping my responses into one because I'm lazy.

Quote Originally Posted by Bikingmomof3
OUCH! If the area does not improve I would most definitely have a doctor look at it. You may be causing blood blisters on top of (under) your existing blisters. It sound like your shoes/socks are not right for your feet. You should not blister that badly. I wish I had more advice.
It really looks like the blister area (which is expanding, but the skin is hardening, and it doesn't hurt as much today) has blood in it. Really creepy and probably pretty gross (sorry ).

Quote Originally Posted by kaybee
Colby, you might want to consider switching shoes or socks if you're getting blisters. Obviously, something is rubbing where it should not. That does not sound like fun!
I have been wearing the same shoes and socks, but this blister is new. I switched to some Smartwool cushioned running socks to see if there's any difference, but I miss my Injiji socks

I was thinking, I think the last time I started to get blisters on this part of my foot, it was time for new shoes. Maybe it's a sign that my feet are working into the shoes "wrong" or aren't being supported anymore and rubbing in someplace they don't rub usually? I have worn these shoes since May, I think... that's 20 miles a week (let's say) for 3 months, then marathon training of 30-40 miles per week for 3 months, so about 660 miles on these shoes.

Quote Originally Posted by Nanci
This is a really great foot care book, with a lot of info on blisters. http://www.fixingyourfeet.com/

The author will also personally offer advice for your particular situation- he's very available.

Also, here is an article on the relationship of blisters/black toenails to electrolyte status. http://succeedscaps.com/blisters.html

I have run the same trail marathon three years in a row, getting nice blisters and losing toenails every year until this last, where instead of trying to watch the clock and take electrolytes I actually set a timer and took them at 30 minute intervals without missing any. I didn't get any blisters- wearing same shoes, same socks, same foot prep, same weather conditions, same course. I'm a believer.
That's VERY interesting about the electrolytes. I lost one toenail when I first started running, and I have one that hurts when I run long distances, but I haven't lost it yet (same toenail as the one I lost but the opposite foot). It may not be a coincidence that I was low on gels the week before last and didn't take them for all of my runs.... and then the blister came. Maybe a combination of shoe support and bad habits. Hmmm. Something to think about. I'll have to be very careful about this in the future.

That book looks great as well, I'll have to see if I can find it.