In this FAQ:

• Side effects of Flow tDCS stimulation
• Skin reactions
• Headache
• Tinnitus
• Worsened symptoms
• Tiredness, fatigue and sleep disturbances
• How do I report a side effect?

Side effects of Flow tDCS stimulation

Less than 5% of Flow users report side effects. The most commonly reported side effects are:

• Skin reactions (pain, redness, irritation, minor burns)
• Headache
• Tinnitus
• Worsened symptoms of depression including increased anxiety
• Tiredness, fatigue and sleep disturbances

It’s important to closely monitor any side effects. They usually get better or go away as your body gets used to the treatment. If you have any concerns or notice anything unusual, contact our support team for help.

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Skin reactions

Skin reactions can include pain, redness, irritation, and minor burns. 

Pain

• You may experience a tingling, itching, or stinging sensation when using Flow. These sensations are common and generally well-tolerated by most users. Read the Stimulating is painful. FAQ for more details.

Redness

• After a stimulation, the area where the headset electrodes were placed might be red. This is because of increased local blood flow to the area. This is normal, and the redness should subside in about an hour.
• You might also notice a pattern of dots on your skin. This happens because of the holes in the refill pads. They will also subside soon.

Irritation

• Skin irritation happens when your skin becomes dry, patchy, scaly, or even cracked. This happens because the outermost protective layer of skin is disrupted from the stimulation.
• Do not stimulate if you have irritated skin. Pause treatment to let your skin completely heal. Hydrate and moisturise your skin.

Minor Burns

• A minor burn could happen if your skin has a strong reaction to the stimulation. This can happen if you stimulate already irritated skin or if the headset electrodes are not placed evenly. For example, if uneven, raised skin is in more direct contact with the refill pads than the rest of your skin.
• Do not stimulate if you have a burn. It should heal naturally on its own. Pause treatment to let your skin completely heal, avoid sunlight, and use SPF 30+ sunscreen.

How do I prevent it?

• Never reuse refill pads: Always use new refill pads to minimise discomfort, irritation, and potential burns.
• Don’t stimulate damaged skin: Make sure the skin underneath the headset electrode area is healthy. Stimulating damaged skin may worsen the condition and cause discomfort.
• Gently clean your forehead before stimulating: Stimulating while wearing makeup or skincare products can cause skin reactions or burns. Don’t clean too vigorously as this can abrade the skin. Use a non-alcoholic soap and pat your forehead dry with a clean towel.
• Apply moisturiser: Use a moisturiser at least twice a day, including after stimulating, to maintain your skin’s natural barrier. Just make sure to remove all skincare products before stimulating.
• Stay hydrated: Drink plenty of water throughout the day to keep your skin hydrated and in optimal condition.
• Make sure the headset is placed correctly: Follow the headset positioning guide and make sure the headset electrodes are placed firmly and evenly on your forehead. Minimise the amount of hair under the electrodes; a small overlap with the hairline is fine. For more guidance on positioning, read the How do I position the headset? FAQ.
• Cool your skin after stimulating: Applying ice packs or a cooling gel can help soothe your skin.
• Pause if needed: If the discomfort becomes too painful when stimulating, you can pause your session and resume later in the day.

Should I continue stimulating?

It's normal to feel mild to moderate pain and see redness or dots on your skin after stimulating. If you experience skin irritation or a burn, wait until your skin has completely healed before stimulating again. Taking this break won't affect your long-term progress.

In almost all cases, skin reactions are mild, and you don't need to see a doctor. For support, email us at support@flowneuroscience.com and include a picture of your skin.

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Headache

Why does it happen?

The cause of headaches is unknown. In our clinical trial, both the active and placebo groups reported about the same number of headaches. This suggests that the headaches are not caused by tDCS, but probably by the tension effect from wearing the headset.

How long will it last?

Headaches are temporary and should subside within a few hours of stimulating. 

How do I prevent it?

• Get in a comfortable position: Find a comfortable position to sit or lie down in before stimulating. It’s common for people to want to keep their head in the same position to avoid any movement of the headset, but this stiffness can cause a headache. Feel free to gently change positions when stimulating.  
• Make sure the headset fits comfortably: The headset should fit securely, but it shouldn't be too tight or press too hard on any part of your head. For more guidance on positioning, read the How do I position the headset? FAQ.
• Relax beforehand: Try to relax before starting your session. Deep breathing or listening to calm music might help reduce anxiety-related headaches.
• Stay hydrated: Drink plenty of water before and after your session. Staying hydrated can help prevent headaches.

How do I treat it?

• Rest and relax: Rest in a quiet place. You can also try a cool cloth on your forehead.
• Pain relief: Over-the-counter pain relievers can help, but it's good to check with a healthcare provider about what's safe for you.

Should I continue stimulating?

If you get a mild headache while stimulating, it's usually okay to finish the session. If the headache is more intense or you prefer to stop, that's fine too. Headaches usually go away as your body gets used to the treatment and by following the prevention tips mentioned above.

If you continue to get headaches after using Flow for a couple of weeks and when following the recommendations above, stop using Flow and talk to your doctor.

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Tinnitus

What is it?

Tinnitus means hearing ringing, buzzing, or other sounds that aren’t actually there. 

Why does it happen?

Tinnitus from using Flow is rare, and the exact causes aren't fully understood. One possible reason is that the headset targets a specific area (dorsolateral prefrontal cortex), but the electric current can sometimes reach parts of the brain that control hearing. Some people are also more sensitive to changes in brain activity which can happen when using Flow, and might notice tinnitus during or after treatment.

How long will it last?

Many Flow users report that their tinnitus goes away over time with continued use of the headset. Usually, it resolves within a day or two. However, a small number of people have experienced tinnitus for more than a week, and sometimes even several weeks after stopping the sessions.

How do I prevent it?

• Make sure the headset is placed correctly: Correct placement helps make sure that the electrical current is directed towards only the intended areas of the brain. For more guidance on positioning, read the How do I position the headset? FAQ.
• Stay relaxed: Stress or tension can sometimes contribute to tinnitus. Try to stay relaxed during your sessions.

How do I treat it?

• Pause the session: If you start hearing ringing or other noises during your stimulation session, stop stimulating. 
• Keep a record: Note down when the tinnitus started and how long it lasted. This information can be helpful if you need to consult your doctor.

Should I continue stimulating?

If you experience tinnitus, you should pause your treatment. When the noises have gone, you can stimulate again.

If tinnitus happens regularly after stimulating or lasts more than a couple of days, stop using Flow and talk to your doctor.

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Worsened symptoms

What is it?

When you start using Flow, you might feel worse or have increased anxiety. These effects can start after a few sessions and usually peak around Weeks 3 to 4.

It's important to know that these worsened symptoms are often temporary. They may be part of an adjustment period while your brain gets used to the stimulation before settling down and possibly showing therapeutic benefits.

Why does it happen?

When using Flow, your brain may need time to adjust to the electrical stimulation, which can lead to temporary changes in mood. This often happens when the treatment is starting to have the desired effect. 

Flow users might also experience worsening symptoms if they feel anxious about the treatment or expect negative effects which can make symptoms worse. This often happens at the end of the Activation Stage (Weeks 1 - 3) when users are anxious to transition to the Strengthening Phase (Weeks 4+), which involves only 2 stimulation sessions per week.

How long will it last?

People may experience worsened symptoms for several days to a few weeks. Even though it might feel like the treatment isn't working, it can actually be a sign that Flow is likely to have a positive effect.

How do I prevent it? 

• Make sure the headset is placed correctly: Correct placement helps make sure that the electrical current is directed towards only the intended areas of the brain. For more guidance on positioning, read the How do I position the headset? FAQ.
• Stay relaxed: Stress or anxiety can lead to worsened symptoms. Try to stay relaxed during your sessions.

How do I treat it?

It’s important to know that sometimes your mood can get worse before it gets better. 

If you feel anxious about switching from the Activation phase (5 sessions per week) to the Strengthening phase (2 sessions per week), please know that you can customise your stimulation schedule under the supervision of a clinician if necessary. Read the How can I stimulate more often? FAQ for more information.

Should I continue stimulating?

If you can tolerate the worsened symptoms, we suggest you keep stimulating as it should get better. If your symptoms get significantly worse to the point of intrusive thoughts or are worse than you've ever experienced before, stop using Flow and talk to your doctor.

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Tiredness, fatigue and sleep disturbances

What is it?

When using Flow, many users have found it helps them sleep better, making it easier to fall asleep and stay asleep. However, some Flow users have also reported feeling more tired, having brain fog, or having trouble sleeping.

Why does it happen?

Flow affects how your brain’s neurons communicate by changing their activity over time, which can disrupt your normal sleep patterns. It can also impact the brain circuits that control sleep, leading to changes in your sleep quality and duration. These disruptions can make you feel more tired and fatigued during the day, even if you spend enough time in bed.

How long will it last?

Changes in energy levels or sleep patterns usually go away within a few hours to a few days. These side effects should disappear as your body adjusts to the treatment.

How do I prevent it?

If using Flow makes it hard to sleep, try having your sessions earlier in the day. Conversely, if it makes you sleepy, scheduling sessions closer to bedtime might help.

How do I treat it?

• Engage in calming activities before bed: It can be useful to engage in calming activities before bed to help counteract any stimulation from Flow, such as reading, listening to soft music, or taking a warm bath. 
• Practice good sleep hygiene: Maintain a regular sleep schedule, limit caffeine and screen time before bed, and ensure your sleeping environment is comfortable and conducive to rest. You can learn more about sleep hygiene principles and sleep as therapy in the Therapeutic Sleep course in the Flow app.

Should I continue stimulating?

Almost all sleep disturbances with Flow are temporary, and the majority of users have found it helps with their sleep cycle. If you can tolerate it, we recommend continuing to stimulate as your body should adapt to the treatment.

If you continue to experience sleep disturbances after using Flow for a couple of weeks and when following the recommendations above, you may want to consider pausing the treatment and talking to your doctor.

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How do I report a side effect?

We encourage all Flow users to report any side effects they experience. To report a side effect, please contact us by submitting a ticket or emailing us at support@flowneuroscience.com.

Disclaimer: Advice, diagnosis and treatment of depression should be conducted under the supervision of a suitably qualified medical professional.