Mastisol Adhesive

I have noticed a variety of posts about using mastisol as an adhesive under the dexcom sensor and some even mentioning using it on top of the sensor cloth pad to reglue when edges coming up. Question for the users: How do you apply it? Spray, brush, q-tip or whatever? Dexcom says to be careful to not apply skinprep of mastisol to the area where the wire penetrates the skin. This seems difficult to do. So anyhow, just looking for a little advice on the best way to use this product and also if there are better alternatives.

I use SKIN-PREP for the entire area under the sensor. I apply Mastisol with a q-tip around the edges during the 2nd week when the edges are coming up.

I also use the SN Skin Prep before and never had a sensor fail as a result. I Dexcom wire never comes in contact with the Skin Prep solution. After 12 days or so depending on use, the edges may start to curl up. I also just use a Q-tip to apply Mastisol under those edges. Let it dry then stick the edges back down. Seal the edge with the Mastisol and you’ll be good to go till the sensor dies. By a 2 0z bottle (not the spray) and it will last many years. Great stuff!

If you’re going to use this stuff, then buy the liquid (not the spray). Do it exactly as Helmut and David described: Drip a couple of drops on to a Q-tip, then wipe both your skin side AND the failing tape where your edges have started to fail. BTW, there’s no need to clean off Dexcom’s “failed goop” before using the Q-Tip: Mastisol dissolves Dexcom adhesive, and your Q-Tip will do the cleaning for you.

VERY IMPORTANT: As David mentioned, You MUST to let it dry almost completely before you stick the tape back down on your skin. (My phrase for this state is “A bit past Gummy”.) If you press the Dexcom pad down while the fluid is still wet, on either side, it absolutely won’t work!

OTOH: Mastisol is pretty nasty stuff, you will need to use an “adhesive cleaner” wipe (such as S&N “Remove”) when you take the Sensor off. Like many others, I have switched to the combination of Skin-Prep under the entire Dexcom area, PLUS another half inch all around, and Flexifix tape on top-- protecting the Sensor pad edges.

Here’s the technique for Skin-Prep: It needs to be absolutely, totally dry (not just “A bit past Gummy”). I recommend a hair dryer on low; keep the dryer pointed slightly upwards into the target area until you see it becoming shiny with nearly microscopic cracks. (Pointing upwards helps to keep the barrier chemicals from flowing downwards due to gravity. Skin-Prep wipes start out extremely runny, and pointing a hairdryer helps to keep the protective film chemicals in place while the IPA carrier fluid evaporates.)

I’ve never put Mastisol under the entire area; only failed edges. But with Skin-Prep, if you remember to dry it out completely before setting the Sensor pad down on your Skin, I’ve never noticed any change in Sensor performance or lifespan – and I don’t think that anyone else here at TD has seen a problem either. Mastisol might be a problem for the wire, but Skin-Prep probably won’t be.

YMMV, of course. You might want to use the “search” box at the upper right corner of these pages to find posts about Flexifix, which many of us use with total satisfaction. (AFAIK, it’s a unique product- the plastic tape is so thin that it stretches with your skin, and springs back with your skin too. That’s why it doesn’t become loose over time.) In years of use, I have never, EVER had a tape failure with this combination of Products (Skin-Prep underneath, Flexfix on top.) Mastisol is nasty, I don’t like it at all.

There’s two ways to use Flexifix: Most people cut four strips, one for each side. My way is more complex; I cut one piece which extends past the Dexcom pad all the way around, and then I cut out a little “window” for Transmitter housing in the middle. Since I’ve had a lot of practice, I can actually cut my “single” just as quickly as other people cut their rectangles. But, if you cut the window really close the size of the Transmitter housing, it’s difficult to put the tape down without creating an accidental fold.

So, if you do it my way, don’t cut your “window” to the same size- make it generously bigger than the housing, so that you have a really easy time putting the tape down.

I’ve been using the Skin Prep plus Flexifix “four strips” method, very successfully. I really put it to the test, with a hot yoga class at least twice a week. The flexifix does flex with me but I usually can’t get past 11 or 12 days with the sensor due to eventual peel up from sweating and showering. I’d rather switch to a new one at that point rather than try to reinforce the old sensor.

I’ve used the mastisol as most of the others below, but I also find that it works okay with the spray bottle. Interesting to hear that it has to be nearly dry to stick well for most, because I’ve noticed that if I put it on right after a shower when my skin is still moist that the glue appears to adhere better! If my skin is initially dry, however, I need to take more time with application and continue to press the edges down with q-tip until totally dry, being careful that the q-tip does not attach and cause the edge to lift. Has anyone tried the other brand; I think that it is called Skintac or surtac or something like that? If so, is it better or worse than mastisol? Look around for d-limonene to use as a solvent (natural orange oil derivative), this may be a bit more gentle than mineral spirits or expensive alternative solvents (much cheaper at about $10/pint). Bob

Skintac is about the same as Mastisol, but a whole lot less expensive, You can apply it with a cotton swab just to the edges of the tape after you place the Dex or pump site. The company will send you a free sample if you call them and ask. Go to If you order it online they ask for a credit card, but if you call them they don’t. They will send remover samples as well. The little bottle that they send you will last a couple of months, so you will know for sure if it works for you before you order it. I buy remover wipes on Ebay. I just snagged a box of 50 Alcare last night for $1.04!

I cut one piece of Flexifix also, rounding the edges and making the cutout in the middle larger than what it needs to be. If the edges start to come up after a week or so, I trim that off and add a strip or two, also with edges rounded.