The Physics of Why Your Serum Decides the Session
Medically reviewed by
4 independent reviewers
Andrew Conrad Barile, PT, DPT
Doctor of Physical Therapy (DPT) | Licensed Physical Therapist (PT) | CEO and Founder, Xtreem Pulse LLC
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Dr. Andrew Conrad Barile is a Doctor of Physical Therapy and the CEO and Founder of Xtreem Pulse LLC, the engineering company behind PureLift. He earned his Doctorate in Physical Therapy from Daemen College and is a licensed physical therapist.
He brings over two decades of clinical and entrepreneurial experience across physical therapy, craniosacral therapy and medical device innovation, built on a working knowledge of human anatomy and muscle physiology.
For PureLift LAB he reviews how current is delivered across all ten levels, from sub-sensory nanocurrent and skin-level microcurrent to motor-level EMS, and how the Infuse pass fits into the same ten-minute routine.
Bertica M. Rubio, M.D.
Board-Certified Physician, Dartmouth Medical School | Medical Director, Antiaging Regenerative Medicine Clinic
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Dr. Bertica M. Rubio is a board-certified physician and Medical Director of the Antiaging Regenerative Medicine Clinic in Redlands, California. She earned her Doctor of Medicine from Dartmouth Medical School and completed her pediatrics residency at UC Irvine Medical Center.
With decades of clinical experience, she specialises in age management medicine, regenerative medicine, wound healing and growth factor therapies, and her practice integrates evidence-based medical science with advanced aesthetic treatment.
For PureLift LAB she reviews articles for medical accuracy across the whole dial, from the gentle nanocurrent and microcurrent settings through to muscle-level EMS and the Infuse pass.
Daniel Grinberg, MD, FACS
Board-Certified Otolaryngologist | Head and Neck Surgeon | Fellow, American College of Surgeons | Mount Sinai
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Daniel Grinberg, MD, FACS is a board-certified otolaryngologist and head and neck surgeon at ENT and Allergy Associates in West Nyack, New York. He earned his medical degree from Columbia University College of Physicians and Surgeons.
He completed his otolaryngology residency at New York University Medical Center, serves as Assistant Clinical Professor at Mount Sinai School of Medicine, and is a Fellow of both the American College of Surgeons and the American Academy of Otolaryngology.
For PureLift LAB he brings a wider clinical lens, connecting at-home facial stimulation from microcurrent to EMS to the anatomy underneath, with the same rigour we apply to every device specification.
Prof. Dr. med. Ivo Buschmann
Chair of Angiology, Medizinische Hochschule Brandenburg | Clinic Director, University Clinic for Angiology
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Prof. Dr. med. Ivo Buschmann is Chair of Angiology at the Medizinische Hochschule Brandenburg Theodor Fontane and Clinic Director of the University Clinic for Angiology at the Brandenburg University Hospital.
He trained at the University of Hamburg, was a Max Planck Society Fellow at the Max Planck Institute for Heart and Lung Research, and held senior consultant posts at the Charite Universitatsmedizin Berlin before his appointment as Chair in 2016.
One of Europe's leading authorities on arteriogenesis, with over 150 peer-reviewed publications and US and EU patents, he reviews for PureLift LAB how the evidence on electrical stimulation is read and where its limits lie.
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Current follows the path of least resistance, and in a facial session that path is the wet layer between the probe and your skin.
This article covers what actually decides the answer, such as:
- Why water conducts and oil does not
- The impedance point
- What a dry patch actually does
- Thickness, which is a separate problem
- What changes the requirement
and many more!
It also explains the single most common complaint about facial devices, which is a session that felt fine for four minutes and then faded.
Key Points:
Water with dissolved salts conducts; oils, silicones and waxes do not.
A dry patch raises resistance there, so current concentrates where the skin is still damp.
Turning the dial up to fix a dry patch sends more current to the wrong places.
This is why an output figure needs an impedance alongside it, and why we publish 500 ohms.
Thickness is a separate problem from chemistry; a heavy water-based cream is still the wrong texture.
Why water conducts and oil does not
Electrical current in tissue is carried by charged particles in solution, principally the salts dissolved in water. Where those are present and mobile, current moves easily.
Oils, silicones and waxes have no free charges to carry a current, so they behave as insulators. A balm between the probe and your skin is an obstacle rather than a medium, which is why an oil-based session feels weak regardless of the level.
That is the whole chemistry of it, and it is why the instruction is a water-based serum rather than a particular brand of one.
The impedance point
Resistance is what current has to push against, and the combination of everything resisting at a given moment is impedance.
Skin impedance varies with how damp it is, where on the face you are working, and whose face it is. Add a dried serum film and the impedance at that spot rises sharply.
This is also why a bare milliamp figure is half a number. PureLift publishes 7 mA at 500 ohms for Face and Pro, 7.7 mA for Pro Edition and 9 mA for Pro Plus and GLOW, with the load stated, because without it the figure cannot be compared against anything.
What a dry patch actually does
It does not simply reduce the current in that spot. Current takes the easiest available route, so it concentrates in the areas that are still damp.
That is why a session that dries unevenly feels patchy rather than uniformly weaker, and why the areas that still feel something can start to feel sharp.
It is also why turning the dial up is the wrong response. You are increasing the total while the distribution is still wrong, which delivers more current to the places that were already receiving it.
Reapply instead. The signal is the probe starting to feel sticky rather than smooth, and it usually arrives sooner than people expect.
Thickness, which is a separate problem
A heavy cream can be water-based and still be the wrong choice, because a thick layer adds distance between the probe and the skin.
What you want is a fluid serum that stays wet for the length of a session and spreads thinly. Hyaluronic acid, glycerin and niacinamide formulations all work.
Plain water fails for a different reason: it conducts perfectly well and evaporates within a minute, giving no glide at all.
What changes the requirement
A heated room in winter drops humidity to levels close to a desert, so serum evaporates faster and reapplication becomes routine rather than occasional.
Post-flight skin behaves the same way for a day or two.
Makeup and sunscreen both sit on the surface by design, so both have to come off before a session rather than being worked through.
Residue on the probe raises resistance from the other side, gradually, which is why cleaning it after every session matters more than it sounds.
The delivery job, which is different again
Conductivity is about carrying current. Delivery is about carrying ingredients, and that is Infuse mode: Infusion opens temporary routes through the outer skin layer and iontophoresis moves charged ingredients along them, with the mechanism set out by Prausnitz and colleagues (10.1073/pnas.90.22.10504).
For conductivity alone the ingredients are irrelevant; water and salts do that work whatever else is in the bottle.
In Infuse mode they matter, which is a reason to choose a serum with actives you want and never to use a strong one in that mode.
The practical summary
Apply more than feels necessary, reapply the moment it drags, and use a fluid water-based serum you already tolerate.
Three minutes per side is the maximum on any PureLift model, and the ten minute session ends on its own.
For the product question, see what a conductive medium does, and for the output numbers, why more microamps alone do not mean better results.
Two related questions come up often alongside this one, and we have answered both in full: how to test whether your own serum conducts, and which gel to use.