Hyperhidrosis affects roughly 4.8% of the US population, or about 15.3 million Americans, according to the most recent peer-reviewed estimate (Doolittle et al., Archives of Dermatological Research, 2016). Globally, that figure puts the number around 385 million people. Of those affected, 70% report severe excessive sweating in at least one body area, and most have never discussed it with a healthcare professional.
If you've just unboxed your Dermadry or you're researching whether to buy one, the practical question is the same: how does it actually work in a session, and what's different about treating your hands, feet, or underarms?
The instructions vary by treatment area. Each one has its own current strength range, session length, and setup. This guide walks through prep, the session itself, progress tracking, and the mistakes most first-time users make. Each treatment area gets its own dedicated section.
What tap water iontophoresis actually does
Tap water iontophoresis has been used to treat excessive sweating since 1936. A small electrical current passes through shallow trays of water (or water-soaked pads for underarms) and through the surface of the skin. Over a series of sessions, this gradually reduces the activity of sweat glands in the treated area.
The exact mechanism isn't fully understood. Current research suggests the electrical current temporarily disrupts the signaling pathway between the nerves and sweat glands, with possible additional effects from changes in pH at the skin surface and partial blockage of the sweat duct openings. What is well-established is that it works: studies cited by the International Hyperhidrosis Society show iontophoresis reduces palmoplantar sweating by approximately 81% and helps about 91% of patients with excessive hand and foot sweating.
Tap water iontophoresis is non-invasive, drug-free, and needle-free. It's typically classified as a first or second-line treatment, recommended for people whose prescription-strength antiperspirants haven't worked, and is a strong option to try before considering invasive options like surgery.
Dermadry is a Health Canada-certified and FDA-cleared Class II medical device for tap water iontophoresis. It treats the hands, feet, and underarms.
Before your first session
A few minutes of prep makes a real difference. Before you set up the device:
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Check your skin. The treatment area should be intact. Cover any small cuts, scrapes, or hangnails with petroleum jelly to insulate them from the current. A Q-tip helps for precise application.
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Remove jewelry. Rings, bracelets, watches, and metal piercings can cause electrical burns where metal touches skin.
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Wash the area with antimicrobial soap. Remove any lotion, deodorant, antiperspirant, or oil that could create a barrier between your skin and the water. For underarm sessions, shaving beforehand also helps the current pass through evenly.
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Dry off completely and have a towel ready for after.
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Get comfortable. Sessions last 15 to 20 minutes, so set up somewhere you can sit still. Feel free to read a book, watch a video, or listen to music during the session.
If your tap water is very soft (low mineral content), the current may not pass through effectively. It’s advisable to use bottled mineral water with at least 150-200ppm as an alternative. Never use distilled or reverse-osmosis water, since both lack the dissolved minerals the current needs to flow.
How to use Dermadry for hands
For palmar (hand) hyperhidrosis, you'll use Dermadry Total or Dermadry Hands & Feet. Both come with two shallow trays plus the controller unit.
Setup
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Place the trays side by side on a flat, stable surface.
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Connect the white cables from the controller to the electrodes in each tray. The device alternates polarity automatically, so don’t worry about cable placement.
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Fill each tray with tap water to a maximum of 250ml. Use water at room temperature or warm (roughly 20 to 40°C / 70 to 105°F).
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The water should cover your palms but not the tops of your hands.
For a video walkthrough of the setup, see:
Running the session
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Power on the controller and select the hands profile.
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Start at the lowest current. Hand sessions run between 1 and 15 mA. First-timers should begin at 1 to 3 mA.
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Hold the activation button for three seconds to begin.
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Place both hands palm-down in the trays.
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Slowly increase the current until you feel a noticeable but comfortable tingle. If it stings or burns, lower it.
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The session runs 20 minutes. The device automatically reverses polarity at the 10-minute mark, and you may feel a brief sensation change. That's expected.
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When the session ends, bring the current to zero before lifting your hands out.
After the session
Pat your hands dry. Apply a fragrance-free moisturizer if your skin feels dry. Mild redness fades within an hour.
How to use Dermadry for feet
For plantar (foot) hyperhidrosis, you'll use the same Total or Hands & Feet trays, just used for your feet. Foot treatment uses the highest current range of any area, since the soles tolerate it well.
Setup
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Place the trays on the floor in front of a chair where you can sit with both feet flat in the water.
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Connect the cables to the electrodes in each tray.
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Fill each tray with enough water to fully cover the soles of your feet, up to 250ml per tray. Make sure it doesn’t reach the tops of your feet.
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Use water at room temperature to warm. Cold water increases skin resistance and reduces effectiveness.
Running the session
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Power on the controller and select the feet profile.
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Start at 1 to 3 mA for your first session. Foot sessions can go up to 25 mA, but work up to your comfort level across several sessions, not all at once.
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Hold the activation button for three seconds.
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Place both feet flat in the trays. The entire sole should be in contact with the water.
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Adjust the current to a strong but comfortable tingle.
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Sessions last 20 minutes, with automatic polarity reversal at 10 minutes.
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Bring the current back to zero before lifting your feet out.
After the session
Dry your feet thoroughly, especially between the toes. Moisturize if your skin feels dry. Calluses on the soles can cause uneven sensation. If one spot feels much more intense than the rest, lower the current rather than pushing through.
How to use Dermadry for underarms
Underarm (axillary) treatment uses Dermadry Total or Dermadry Underarms. Instead of trays, you use water-soaked pads with electrodes that sit under each arm.
Setup
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Soak the underarm pads thoroughly in tap water. They should be saturated but not dripping. Don't drown them, since excess water just runs down your sides.
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Slide the electrodes into the pads.
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Connect the cables to the controller.
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Sit upright in a chair where you can rest your arms at your sides for the full session.
During the session
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Power on the controller and select the underarms profile.
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Underarm sessions run between 1 and 8 mA. The skin under your arms is much thinner than your palms or soles, so your comfort threshold will be lower. Start at 1 mA.
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Place a soaked pad firmly against each underarm, with full skin contact. The pads sit lengthwise along the underarm, not across. Getting the orientation wrong is one of the most common first-time mistakes.
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Lower your arms snugly against your sides to hold the pads in place. A loose-fitting tank top or t-shirt with the sleeves rolled up works well.
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Hold the activation button for three seconds to begin.
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Increase the current slowly to a comfortable tingle. If one side feels stronger than the other, the weaker pad probably isn't fully in contact. Reposition the pad rather than turning up the current.
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Sessions last 15 minutes. Polarity reverses every 2 minutes 30 seconds, so you'll feel a few brief sensation changes during the session.
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Bring the current to zero before removing the pads.
After the session
Wipe down with a clean towel. Skip deodorant for an hour or two if your skin feels sensitive. Hold off on antiperspirant right after a session, since the skin barrier is briefly more permeable.
What a session should feel like
A typical session feels like a steady tingle or pins-and-needles sensation. As you increase the current, the feeling gets more intense. The right level for you is the highest current you can hold comfortably for the full session, not the highest you can briefly tolerate.
What's normal:
- Mild tingling that intensifies briefly after polarity reverses
- Slight redness on the treated skin afterward
- A warm or buzzing sensation during the session
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Temporarily dry or tight-feeling skin
What means you should lower the current or stop:
- Sharp burning or stinging in one spot (usually a small cut you missed; cover it with petroleum jelly)
- Visible blistering during or right after a session
Common first-week mistakes
These are the three errors that account for most "Dermadry isn't working" complaints in the first week. None of them are actually device problems.
1. Setting the current too low and staying there. The most common reason people don't see results in week one is that they set the current at 3 mA on the first session, find it tolerable, and never increase it. Iontophoresis works best at the highest current you can comfortably hold. The British Association of Dermatologists confirms this in their patient guidance: better outcomes are linked to higher currents.
The fix: increase by 1 mA per session. Each session, raise the current by one milliamp until you reach an intense but not painful tingle. Hold there. Back off only if you develop irritation or redness that doesn't fade. For most users, the high efficacy level is somewhere between 6 and 15 mA for hands, 16 and 25 mA for feet, and 5 and 8 mA for underarms.
2. Using the wrong water. If you live somewhere with very soft water (common in cities with water softeners or in certain regions), the current can't flow effectively through the trays. The user feels little to no sensation, assumes the device is broken, and gives up.
The fix: switch to bottled mineral water. Distilled and reverse-osmosis water won't work at all. If the device still won't run a current, Dermadry's troubleshooting guide for device startup issues covers the next steps.
3. Doing too few sessions in the initial phase. Some do sessions every other day, while some only do 2-3 days of consecutive sessions. Too few sessions in the initial phase can fail to build the skin’s response to the treatment. What many find successful is 5 days of treatment sessions, with two days of rest after. Depending on the severity of sweating, you can do this 2-6 weeks to achieve dryness. Once dry, switch to maintenance and reduce the number of sessions. Consistency is key.
4. Pad orientation for underarms. The underarm pads need to sit lengthwise along the underarm, oriented up and down, not sideways across it. Getting this wrong is extremely common on session one. The session technically still runs but the contact area is much smaller, and results suffer.
Other less-common but worth mentioning: deodorant residue creates a barrier (always wash with antimicrobial soap before underarm sessions), heavy underarm hair can interrupt the current (shaving helps), and pads that are dripping wet rather than thoroughly saturated lose contact as the water runs off.
Initial phase and maintenance phase
Dermadry treatment runs in two phases.
Initial phase. Five sessions per week for about two weeks, with two rest days for the skin to recover. This is what gets you to dryness. Some users see results within two weeks. More severe cases may need up to six weeks of daily sessions to fully respond.
Maintenance phase. Once you're dry, drop down gradually. Most users land somewhere between one to three sessions per week, depending on severity. Don't drop straight to maintenance the moment you see results, since sweat tends to come back before you have time to react. Step down gradually and find the lowest frequency that keeps you dry.
If you stop entirely, dryness lasts up to six weeks. Maintenance is ongoing, but each session is short enough to fold into an evening routine. For a deeper breakdown of the recommended cadence, see Dermadry's full treatment schedule guide.
Treating multiple body areas
This is the part most "how to use" guides skip, and it's the section that matters most if you sweat in more than one area.
According to Glaser et al. (Dermatologic Surgery, 2016), 81% of people with axillary hyperhidrosis report three or more affected body sites, and 46% report four or more. If you sweat in multiple areas, you have what's called multifocal hyperhidrosis, and there's a good chance you bought a Dermadry Total to cover all of them.
The good news is that you can do all three treatments in one day over three separate sessions. The hands and feet sessions are 20 minutes each, and underarms takes 15 minutes, totaling 55 minutes.
When treating multiple areas, ensure that you only use one device at a time. Two devices can interfere with each other, and lead to diminished results or other complications.
Also, note that each area reacts differently, so the length of treatment phases in each area may vary. For example, hands may reach 100% dryness within two weeks, while underarms might take four. Hands may need only one or two maintenance sessions per week, but feet might need three.
It’s a case-by-case basis, so it’s important to determine what works best for your schedule and your skin.
How to tell it's working: HDSS scoring
The Hyperhidrosis Disease Severity Scale (HDSS) is a one-question, validated scale used in clinical research. Score yourself for each affected area, weekly, throughout your initial phase.
Pick the statement that best describes your sweating:
- — My sweating is never noticeable and never interferes with my daily activities.
- — My sweating is tolerable but sometimes interferes with my daily activities.
- — My sweating is barely tolerable and frequently interferes with my daily activities.
- — My sweating is intolerable and always interferes with my daily activities.
A 1-point improvement (for example, from 4 to 3) corresponds to roughly a 50% reduction in sweat production. A 2-point improvement corresponds to roughly an 80% reduction.
A practical tracking template:
- Week 0 (before first session): ___
- Week 2: ___
- Week 4: ___
- Week 8: ___
Most users see at least a 1-point improvement by week 2 and reach a score of 1 or 2 by week 4 to 6. If you're not seeing any movement after two weeks of consistent daily sessions at a comfortable working current, that's the point to revisit the soft-water test, check pad orientation, or contact Dermadry support.
Troubleshooting
I don't feel anything, even at a higher current. Check that the cables are fully plugged in. Make sure your skin is fully in contact with the water or pads. If your tap water is very soft, switch to bottled mineral water.
The current feels uneven, stronger on one side. For hands and feet, check that both sides have equal water depth and skin contact. For underarms, reposition the pad on the weaker side. Don't increase the current to compensate, or you'll overload the side that's already working.
My skin is red, dry, or itchy after sessions. Some redness is expected. Apply a fragrance-free moisturizer after each session. If a specific spot stays red at the waterline, dab a small amount of petroleum jelly there before your next session. For persistent mild irritation, 1% hydrocortisone cream (over-the-counter) helps. Stop treatment if you develop blisters or persistent itching, and resume once skin recovers fully.
I'm sweating more than before. A small share of users see a brief uptick in sweating during the first few sessions. It’s a normal reaction as the skin adjusts to the treatment, and goes away on its own with continued sessions.
I have a cut, scrape, or hangnail. Cover it with petroleum jelly before your session to insulate it. If the cut is large or deep, wait until it heals before treating that area.
The device won't start. Verify the AC adapter is fully plugged in, the cables are seated in the controller, and the electrodes are correctly placed. You can also use warm water to help the current flow more freely through your skin. If you've recently shaved or applied deodorant before an underarm session, residue can interfere with current flow. Wash with antimicrobial soap and try again. For a full diagnostic checklist, see Dermadry's startup troubleshooting guide.
What iontophoresis costs compared to other first-line treatments
Most people with hyperhidrosis start with clinical-strength antiperspirants containing aluminum chloride hexahydrate (products like Drysol or Certain Dri). These run $10 to $30 per month, and for mild cases, that’s often enough. For moderate to severe sweating, though, antiperspirants alone typically aren’t sufficient, and the next question becomes: what do you do when the first-line topical option stops working?
Iontophoresis is typically the next step. It’s classified as a first or second-line treatment in most dermatological treatment algorithms, and it has a major practical advantage: you own the device and do treatments at home. No recurring clinic visits, no appointment scheduling, no co-pays per session.
Here’s the cost breakdown. A Dermadry Total is a one-time purchase that treats hands, feet, and underarms. The controller, AC adapter, and cables carry a 5-year warranty. After the initial purchase, the only ongoing costs are replacement consumables (pads, electrodes, and mats) as they wear out. Compare that to prescription antiperspirants at $10 to $30 per month ($600 to $1,800 over five years), and the device pays for itself within the first year or two for most users.
The at-home angle matters for more than just cost. Clinic-based iontophoresis exists, but it means multiple appointments per week during the initial phase and ongoing visits for maintenance. With a home device, you fold sessions into your evening routine on your own schedule. That consistency is actually what makes iontophoresis work well: the people who get the best results are the ones who can stick to the recommended cadence without the friction of booking appointments.
For a fuller comparison of where iontophoresis fits alongside other treatment options, see Dermadry’s guide to treating hyperhidrosis.
Insurance, HSA, and FSA
Dermadry's merchant category code (5047) qualifies it for HSA and FSA reimbursement under most plans. For health insurance reimbursement specifically:
- CPT code 97033 covers iontophoresis treatment, billed in 15-minute increments.
- Iontophoresis devices are typically classified as durable medical equipment.
- Major insurers including Aetna, Cigna, Tricare, Humana, UnitedHealthcare, and Blue Cross Blue Shield plans have reimbursed iontophoresis devices for hyperhidrosis.
- Dermadry doesn't bill insurance directly. The standard workflow is to purchase out-of-pocket, then submit for reimbursement with a Letter of Medical Necessity from your dermatologist.
The International Hyperhidrosis Society publishes a free Dermadry Insurance Reimbursement Guide including a Letter of Medical Necessity template.
Using Dermadry for Pregnancy, Teens, Travel, and Sensitive Skin
Pregnancy. Iontophoresis is contraindicated during pregnancy, not because of known harm but because long-term safety studies in pregnant patients haven't been done. Most users pause treatment for the duration of pregnancy and resume postpartum. According to the British Association of Dermatologists, iontophoresis is generally considered safe to resume while breastfeeding, as long as sessions aren’t done simultaneously with feeding.
Children and teens (ages 13 and up). Dermadry is indicated for users aged 13 and older. About 66% of palmar and 61% of plantar hyperhidrosis cases begin before age 12, so adolescent treatment is medically common. In the US, the device must be purchased by an adult aged 21 or older. For children younger than 13, iontophoresis can still be appropriate, but should be coordinated with a dermatologist.
Travel. The Dermadry AC adapter is rated 100 to 240 V, 50 to 60 Hz, so it works in any country with only a plug adapter (no voltage converter needed). For trips longer than a week, a practical strategy is to do one extra session 1 to 2 days before departure to extend dryness through the trip, then resume normal cadence on return. Alternatively, the device is portable and durable enough to bring with you.
Sensitive skin, eczema, or psoriasis. Active eczema or psoriasis patches in the treatment area are a relative contraindication during flares. The current can concentrate on breaks in the skin barrier, leading to a sharp sensation during treatment and delaying the skin’s healing process. If you have sensitive skin generally, start at lower currents (1 to 2 mA), use petroleum jelly on any areas of irritation at the waterline, and apply a fragrance-free moisturizer after each session.
Skipped weeks. If you miss a week of treatment, don't double up sessions in a single day. Return to two or three sessions for the first week back, then taper to your regular maintenance schedule.
Turn Session Time Into Time Well Spent
A 15- to 20-minute session gives you a nice pocket of time to relax with something you enjoy or get a quick task done. Here are some practical options by area:
- Hands: audiobooks, podcasts, music, voice-dictated emails, hands-free video calls, watching TV.
- Feet: laptop work, reading, writing, phone calls, eating a meal.
- Underarms: arms are pinned to your sides, so audio-only content (podcasts, music, calls on speaker), books, and mobile apps are realistic options.
For more tips on building treatment into your routine, see Getting the Most Out of Your Iontophoresis Treatments.
Safety and contraindications
Talk to your doctor before using Dermadry if any of the following contraindications apply:
- Cardiac pacemaker
- ICD (implantable cardioverter defibrillator)
- Suspected or diagnosed heart problems (e.g. cardiac arrhythmia)
- Seizure disorders (epilepsy)
- Pregnant or suspected pregnancy
- Metal-containing intrauterine device (IUD)
- Metallic implants
- Large skin lesions and lesions that cannot be covered with petroleum jelly
- Numbness in the treated areas
- Infections or irritated skin
- Impaired sensation in hands, underarms or feet (e.g. polyneuropathy)
- Malignant disorders in the area of application
- Severe vascular disorders (e.g. local inflammation or thrombosis)
The Dermadry treatment can be used even if you are/have:
- Have metal implants that are far away from the area you are treating with Dermadry.
- Undergoing laser treatment(s)
- Have dental implants or prosthetics
- On birth control (excluding copper IUDs)
- Have metal jewelry on any part of your head (such as earrings or nose rings)
- Breastfeeding (although it is not recommended to do an iontophoresis treatment simultaneously)
- Going to the gym
If in doubt, contact your health professional.
Possible side effects are temporary and include skin reddening, tingling, stinging, small blisters, itching, and brief muscle numbness. These typically resolve on their own. If you notice an allergic reaction (red, bumpy, scaly, or swollen skin) at the contact points, stop treatment and contact Dermadry support.
Frequently asked questions
How long until I see results? Most users notice reduced sweating within 6 to 10 sessions (two weeks). Some see results sooner; severe cases may take longer. Stick with the daily schedule for the full initial phase to evaluate effectiveness.
Can I use Dermadry every day? No, not everyday. During the initial phase, the recommended schedule is 5 times per week with two rest days. This routine gives your skin the time it needs to rest and recover.
Do I need a prescription? Dermadry is FDA-cleared and Health Canada-certified for home use. A prescription is required for purchase only in the USA. A prescription or Letter of Medical Necessity is helpful if you plan to seek insurance reimbursement.
Can I share my Dermadry with family members? No. Dermadry is designed for single-use, and sharing devices and accessories among individuals is not advised for safety and hygiene reasons.
What kind of water should I use? Standard tap water works for most users. If your water is very soft or runs through a softener, switch to bottled mineral water with at least 200ppm. Never use distilled or reverse-osmosis water.
Can I do hands and feet in the same session? No, treatments must be completed one at a time. Even if you have two devices, treating your hands and feet simultaneously alters the calibrated electrical flow, which reduces the treatment's effectiveness and increases the risk of side effects. To ensure safe, optimal results, always perform your hand and foot sessions as entirely separate treatments.
Will my sweating come back if I stop? Dryness can last up to six weeks without maintenance. With maintenance sessions, you can keep the dryness for as long as you need.
Does it work for face or back sweating? Dermadry's electrodes and pads are designed for hands, feet, and underarms specifically. It isn't indicated for craniofacial or trunk hyperhidrosis.
How long does the device last? The controller, AC adapter, and cables have a 5-year expected service life and a 5-year warranty. Consumables (pads, electrodes, mats, towels) are replaced as needed. Underarm pockets typically need replacement after 30 sessions.
Pick the Dermadry Model for Your Sweat Areas
The right Dermadry model depends on where you sweat:
- Hands, feet, or both: Dermadry Hands & Feet
- Underarms only: Dermadry Underarms
- All three areas: Dermadry Total
If you sweat in multiple areas (and statistically, most people with hyperhidrosis do), Total gives you the most flexibility for the smallest cost difference.
For setup videos, troubleshooting beyond the basics, and direct support, Dermadry's customer support team is available 24/7. To connect with others living with the condition, Dermadry maintains a list of hyperhidrosis communities and resources, including the r/hyperhidrosis subreddit and the Voices of Hyperhidrosis awareness campaign.
Sources: Doolittle J, Walker P, Mills T, Thurston J. "Hyperhidrosis: an update on prevalence and severity in the United States." Archives of Dermatological Research, 2016. Glaser DA et al. "Prevalence of Multifocal Primary Hyperhidrosis." Dermatologic Surgery, 2016. Dolianitis C et al. "Iontophoresis with glycopyrrolate for the treatment of palmoplantar hyperhidrosis." Australasian Journal of Dermatology, 2004. Pariser DM, Ballard A. Dermatologic Clinics, 2014. International Hyperhidrosis Society. British Association of Dermatologists patient leaflet on iontophoresis. Dermadry Support Center.