Duct Tape - any negatives for blister protection?

You can also try using moleskin and cut a donut hole in it slightly larger than the blister itself....cut the moleskin to fit the entire bottom of your forefoot region but then cut out a circle.  good luck

btw: the reason for this is it will remove the friction for the area so you can run pain free and friction free

I used to do long (competitive) road marches in the Army.  Out in White Sands, I got a blister on mile 8 and threw a patch of moleskin on and was able to finish the next 17 miles no problem.

Moleskin has always worked well for me.

I can't get duct tape to stick to my skin once it's damp, and it tends not to stay on once it's damp either.

Got to heal up the blister before you try other lube options; in the meanwhile, cover. What everyone else said ... moleskin, Tegaderm, even SuperGlue.

When it comes to long runs or races, stuff like BodyGlide and Aquaphor haven't worked for me at all. I use SportShield Roll-On.

The biggest problem with duct tape is that it's a vapor barrier. It's not permeable because of the adhesive. As a result, your skin tends to degrade under the tape. Once you put it on, you're married to it.

Here is a look at my feet from a 154 mile run in the sahara as they died under the tape:

I've had success with white athletic tape from the drug store. This material is breathable vs. duck tape which isn't.

Duck tape works well too. I cut out a small piece to cover the wound, and reverse that onto the larger piece so it doesn't stick to the blister or wound area. I have also stuck gauze on the duct tape, which works nice. 

i can't speak to 154mi desert runs,

but duct tape has been a terrific solution for 26.2.

I used to use it all the time in races. The trick for me was to find the thinner duct tape. The really thick silver stuff wouldn't form to my foot and would come off mid swim. The thinner stuff worked much better.

x2
I used it for blisters acquired a week or 2 before an inline skating marathon and it worked wonderfully.