Float Tank Centers Side Effects and Risks: What You Need to Know [2026]

Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting float therapy, especially if you have pre-existing medical conditions. Some links in this article may be affiliate links — we may earn a commission at no extra cost to you.

Understanding Float Tank Therapy: A Quick Primer on What Happens to Your Body

Before we get into what can go wrong, it helps to understand what's actually happening when you step into a float tank. You're climbing into roughly 10 inches of water saturated with 800-1,200 pounds of Epsom salt (magnesium sulfate). The water is heated to skin temperature — about 93.5°F — and you're sealed in a lightless, soundless environment for 60 to 90 minutes.

Your body does some interesting things in response. Without gravity pulling on your joints and muscles, your proprioceptive system — the internal sense that tells you where your body is in space — essentially goes quiet. Your heart rate drops. Cortisol levels decrease. Blood pressure tends to fall. Your brain shifts from beta wave activity (normal waking consciousness) into theta waves, the same state you experience in that fuzzy zone between waking and sleep.

This is called Reduced Environmental Stimulation Therapy, or REST. Researchers at the Laureate Institute for Brain Research (LIBR) have been studying float-REST extensively since 2016. Their work, led by Dr. Justin Feinstein, has shown measurable reductions in anxiety, stress, and muscle tension — even after a single session. A 2018 study published in PLOS ONE involving 50 participants with anxiety and stress-related disorders found significant post-float reductions in stress, muscle tension, pain, and depression, with increases in serenity and overall well-being.

But here's the thing. Any intervention powerful enough to produce real physiological changes is also powerful enough to produce side effects. The same sensory reduction that calms an anxious mind can disorient someone who wasn't prepared for it. The same Epsom salt that relieves muscle soreness can sting an open cut you forgot about. The same darkness that promotes theta-wave relaxation can trigger panic in someone with undiagnosed claustrophobia.

Float therapy is safe. But "safe" and "zero risk" aren't the same thing. Centers like Just Breathe Salt Spa in Philadelphia and Levity take safety seriously — pre-session screenings, detailed orientations, emergency call buttons inside every tank. Good float centers build safety into the experience. But you still need to know what you're walking into.

Let's break down every documented side effect and risk, what the research actually says, and how to minimize your chances of a bad experience.

The Most Common Side Effects (And Why They Happen)

Most float tank side effects fall into the "annoying but harmless" category. They're temporary, they're manageable, and they usually don't happen again once you know what caused them. But they can catch you off guard if nobody warned you.

Nausea and Dizziness

This is probably the most commonly reported side effect, especially among first-time floaters. Research suggests it affects roughly 10-15% of people during their first session. The cause is straightforward: your vestibular system (the inner-ear mechanism that controls balance) gets confused when it can't reconcile the signals it's receiving. You're floating, so there's no pressure on your body telling it which way is "down." Your eyes are closed in total darkness, so there's no visual reference point. Your inner ear is the only system still trying to orient you — and without backup from your other senses, it can misfire.

The result feels like mild motion sickness. Some people describe it as the sensation of slowly spinning, even though they're perfectly still. Others feel a wave of queasiness that passes within a few minutes.

How to minimize it: Keep your eyes open for the first few minutes (even in darkness, having them open helps). Touch the walls of the tank periodically to give your brain a spatial reference. If you feel nauseous, bend your knees slightly to change your body position. Most people find this resolves within the first 15 minutes as the brain adapts.

Skin Irritation and Salt Sensitivity

Eight hundred pounds of Epsom salt creates a solution that's roughly 30% magnesium sulfate. That's dense. For context, seawater is about 3.5% salt. You're floating in something nearly ten times more concentrated.

For most skin types, this is actually beneficial — magnesium absorption through the skin has been shown to support muscle recovery and may reduce inflammation. But for some people, it causes problems:

Open cuts, scrapes, or fresh shaving nicks will sting. Not dangerous, but uncomfortable enough to ruin your session. Most float centers provide petroleum jelly to seal small cuts before you get in.
Eczema, psoriasis, or dermatitis can flare up. The concentrated salt can dry out already-compromised skin barriers. Some people with mild eczema report improvement; others report worsening. It's unpredictable.
Recently waxed, sunburned, or chemically treated skin (fresh chemical peels, retinol users) may react to the salt concentration.
Contact lens wearers who accidentally get salt water in their eyes will experience significant stinging. Always remove contacts before floating.

A 2022 survey of 1,500 float center customers found that skin-related complaints accounted for approximately 23% of all reported side effects, making it the most frequently mentioned category.

Post-Float Disorientation

When you step out of a float tank after 60-90 minutes of zero sensory input, the real world hits differently. Lights seem brighter. Sounds seem louder. Your body feels heavier — because gravity is suddenly back. This sensory re-calibration period typically lasts 10-20 minutes.

Most people describe it as pleasant — a dreamy, spaced-out feeling. But for some, especially first-timers, it can be genuinely disorienting. A few people report feeling "off" for several hours afterward, with mild cognitive fogginess or difficulty concentrating.

This is why reputable float centers like Zen Den in Boston include a post-float decompression area with soft lighting and tea. They build the re-entry into the experience. Don't schedule anything demanding immediately after your first float — give yourself at least 30 minutes to acclimate.

Heightened Sensory Sensitivity

Related to disorientation but distinct enough to mention separately. After extended sensory deprivation, your nervous system temporarily recalibrates its sensitivity thresholds. Sounds that wouldn't normally bother you can feel jarring. Fluorescent lights can feel harsh. Even the texture of your clothing might feel unusually noticeable against your skin.

This heightened sensitivity usually fades within an hour. Some float enthusiasts actually chase this effect — they find that music sounds better, food tastes richer, and colors look more vivid after a float. But if you're not expecting it, walking out of a float center into a busy urban street can be overwhelming.

Psychological Side Effects: When Silence Gets Loud

This is where float therapy gets more nuanced. The physical side effects are predictable and well-understood. The psychological ones are more variable, more personal, and — in rare cases — more concerning.

Anxiety and Panic Responses

Here's an uncomfortable statistic: approximately 5-7% of first-time floaters experience some form of anxiety or panic during their session, according to data compiled from multiple float center intake surveys across the U.S. and Canada.

The mechanism is simple. When you remove all external stimulation, your brain has nothing to process except its own internal activity. For some people, that means racing thoughts. For others, it means confronting emotions or memories they've been avoiding. For people with undiagnosed anxiety disorders, the silence can amplify the anxious inner monologue they normally drown out with activity and noise.

Claustrophobia is the most obvious trigger. Even people who don't consider themselves claustrophobic can feel uneasy in a closed float pod. The good news: most modern float centers offer open float pools and cabin-style tanks alongside traditional pods. If enclosed spaces make you nervous, you have options. Our complete guide to float tank types covers the differences in detail.

But claustrophobia isn't the only psychological trigger. Some floaters report:

Intrusive thoughts that feel louder and more persistent in the silence
Emotional releases — crying, grief, or anger surfacing unexpectedly
Mild hallucinations — seeing colors, patterns, or shapes in the darkness (this is actually normal and related to the brain generating its own visual input in the absence of external light, a phenomenon called the Ganzfeld effect)
Time distortion — some people feel like 10 minutes have passed when it's been 45, or vice versa. This isn't dangerous but can be unsettling.

The "Worse Before Better" Pattern

Float therapy researchers have documented something interesting: for people dealing with chronic stress or anxiety, the first 1-3 sessions can actually feel uncomfortable. Dr. Justin Feinstein's research at LIBR noted that participants with anxiety disorders often reported initial discomfort that decreased significantly by their third or fourth float. The body and mind need time to learn how to "let go" in the tank.

This is important context. If your first float was stressful, that doesn't necessarily mean float therapy isn't for you. It might mean your nervous system is so wound up that the sudden absence of stimulation is itself stressful — and that subsequent sessions may be markedly different. Our beginners guide walks through how to prepare mentally for your first session.

Depersonalization and Derealization (Rare)

In very rare cases — the research literature puts this at well under 1% of floaters — people report brief episodes of depersonalization (feeling detached from your body) or derealization (feeling like the world isn't quite real) after floating. These episodes are typically brief, lasting minutes to hours, and resolve on their own.

However, for people with a history of dissociative disorders, depersonalization disorder, or certain psychotic-spectrum conditions, float therapy may exacerbate these symptoms. This is one of the few situations where float therapy carries a genuinely meaningful psychological risk, and it's why pre-screening questionnaires at good float centers ask about psychiatric history.

If you have a history of psychosis, schizophrenia, or dissociative disorders, talk to your mental health provider before trying float therapy. This isn't a blanket prohibition — some clinicians actually use float therapy therapeutically with these populations — but it requires professional guidance.

Who Should Not Float: Medical Contraindications

Float therapy doesn't have a long list of absolute contraindications, but the ones that exist are important. Here's what the clinical literature and float industry safety standards agree on.

Absolute Contraindications (Do Not Float)

Uncontrolled epilepsy or seizure disorders. The risk here is drowning. If you have a seizure in a float tank — even in 10 inches of water — aspiration is possible. The highly concentrated salt water makes aspiration particularly dangerous to the lungs. People with well-controlled epilepsy (seizure-free for 12+ months on stable medication) may be cleared by their neurologist, but this requires medical authorization.

Active, open wounds or severe skin infections. Beyond the pain of salt in an open wound, there's an infection risk in both directions — your wound could introduce pathogens to the tank, and (despite filtration systems) you could theoretically pick up something from the water. This includes recent surgical incisions, active herpes outbreaks, impetigo, and any weeping dermatological condition.

Severe kidney disease. The magnesium in Epsom salt is absorbed through the skin. In healthy individuals, the kidneys efficiently excrete any excess magnesium. But in people with significantly impaired kidney function (GFR below 30), this transdermal magnesium absorption can contribute to hypermagnesemia — a potentially dangerous elevation of blood magnesium levels. Symptoms include nausea, muscle weakness, and in severe cases, cardiac arrhythmias.

Active psychosis or acute psychiatric crisis. Sensory deprivation can intensify psychotic symptoms. Someone in the midst of a psychotic episode, severe manic episode, or acute PTSD flashback should not be in a float tank.

Incontinence (bowel or bladder). This is a practical hygiene issue rather than a medical risk to the individual, but float centers will (and should) decline to serve anyone who cannot maintain bowel and bladder control for the duration of a session.

Relative Contraindications (Float With Caution)

Pregnancy. This is debated. Many float centers welcome pregnant women, especially in the second and third trimesters, and anecdotal reports are overwhelmingly positive — the buoyancy relieves the weight of the belly, and the relaxation is profound. However, there are no large-scale clinical studies on float therapy during pregnancy. The elevated water temperature (93.5°F) is well below the threshold associated with neural tube defects (above 101°F), so hyperthermia isn't a concern. But first-trimester floating is generally discouraged due to the general medical conservatism around early pregnancy interventions.

Low blood pressure. The relaxation response triggered by floating can further lower blood pressure. If you already run low (systolic below 90), you may feel lightheaded or faint when standing up after a float. Rise slowly and stay in the post-float area until you feel stable.

Claustrophobia or severe anxiety disorders. Not a medical contraindication per se, but a practical one. As discussed above, open float pools are an alternative. Starting with the lid/door open and the light on is another option. But forcing yourself through a panic attack in a float tank is counterproductive.

Recent hair dye or color treatment. The salt can strip color from freshly dyed hair. Most centers recommend waiting at least 7 days after coloring. This won't hurt you — but it'll hurt your highlights.

Ear infections or perforated eardrums. Salt water in the middle ear is painful and can worsen infections. Use the provided earplugs, or postpone if you have an active infection.

Water Quality and Hygiene: The Risks You Can't See

Let's talk about what's in the water. This is a legitimate concern, and one that separates great float centers from mediocre ones.

How Float Tanks Stay Clean

The high salt concentration itself is inhospitable to most bacteria — the 30% magnesium sulfate solution creates an environment where most pathogens can't survive. But "most" isn't "all," and Epsom salt alone isn't sufficient sanitation.

Industry-standard float tank hygiene involves a multi-layered approach:

UV sterilization — Ultraviolet light kills bacteria, viruses, and other microorganisms as water passes through the filtration system. This is the primary sanitation method used by most modern float tanks.
Hydrogen peroxide — Many systems use a low concentration of H₂O₂ (typically 30-100 ppm) as a secondary disinfectant. It breaks down into water and oxygen, leaving no chemical residue.
Ozone treatment — Some higher-end systems inject ozone (O₃) into the water. Ozone is a powerful oxidizer that destroys organic contaminants.
Micron filtration — The water is pumped through filters (typically 1-10 micron) between each session to remove particulate matter.
Complete turnover — The entire volume of tank water passes through the filtration system 3-4 times between sessions. This is an industry standard established by the Float Tank Association.

According to the Float Tank Association (now the Float Tank Industry Council), properly maintained float tanks turn over and filter 100% of their water volume a minimum of three times between each client. Testing protocols recommend checking pH (target: 7.0-7.4), specific gravity (1.25-1.30), and oxidizer levels before each business day.

What Could Go Wrong

The risks emerge when maintenance protocols aren't followed rigorously:

Pseudomonas aeruginosa — This opportunistic bacterium can survive in high-salt environments and causes folliculitis (hot tub rash), ear infections, and UTIs. It's the most commonly cited pathogen risk in float tanks. Proper UV and hydrogen peroxide protocols eliminate it.
Legionella — Theoretically possible in any warm-water system, though no documented cases in float tanks exist in the published literature. UV treatment is effective against it.
Chemical sensitivity — Some people react to hydrogen peroxide or bromine (used in some older systems) in the water. Symptoms include skin redness, itching, or respiratory irritation.

How to Evaluate a Float Center's Hygiene

Ask questions. A good center will welcome them. A center that gets defensive about hygiene questions is a red flag.

What filtration system do you use? Look for: UV + H₂O₂ or UV + ozone. Chlorine-based systems are outdated for float tanks and can cause skin and eye irritation.
How many times does the water turn over between clients? Minimum acceptable answer: 3 times. Many premium centers do 4-5.
Do you test water chemistry daily? The answer should be yes, without hesitation. Ask to see their log if you want — legitimate centers keep one.
How often do you drain and deep clean? Industry standard is a full drain and scrub every 3-6 months, with weekly or biweekly supplemental deep cleans.

Our myths debunked article covers the hygiene question in more detail, including why "float tanks are dirty" is largely a myth at well-run facilities.

Drug Interactions and Medication Concerns

This is an under-discussed area. Float therapy interacts with certain medications in ways that aren't always obvious, and most online float resources barely mention it.

Blood Pressure Medications

Floating lowers blood pressure. If you're already taking antihypertensives — ACE inhibitors, beta-blockers, calcium channel blockers, or diuretics — the combined effect can cause hypotension. Symptoms include dizziness, lightheadedness, blurred vision, and fainting, especially when standing up after a session.

This doesn't mean you can't float on blood pressure medication. It means you should:

Tell the float center staff what you're taking
Rise very slowly after your session
Stay in the post-float area until you feel stable
Consider scheduling your float at a time when your medication levels are at their trough (typically right before your next dose)
Discuss with your prescribing physician, especially if your blood pressure is already on the low end of controlled

Insulin and Diabetes Medications

The relaxation response can affect blood glucose levels. The magnesium absorption from Epsom salt may also improve insulin sensitivity. For people on insulin or sulfonylureas, this combined effect could potentially cause hypoglycemia. If you're diabetic:

Check your blood sugar before and after floating
Bring a snack for the post-float period
Don't float if your blood sugar is already trending low
Inform center staff of your condition

Psychiatric Medications

SSRIs, SNRIs, benzodiazepines, and antipsychotics can all interact with the float experience in unpredictable ways. There's very little formal research on this. Anecdotally, some people on SSRIs report reduced emotional intensity during floats, while others report heightened emotional responses. Benzodiazepines may amplify the sedative quality of floating to the point of falling asleep in the tank — which, while not typically dangerous (the salt keeps you buoyant even if fully relaxed), is worth being aware of.

If you're on psychiatric medication, float therapy is not contraindicated — but mention it to your prescriber, especially if you're adjusting doses or starting a new medication.

Transdermal Medications

Patches (fentanyl patches, nicotine patches, hormone patches) should be removed before floating. The warm water and prolonged soaking can alter absorption rates, potentially delivering more medication than intended. The salt solution can also degrade the adhesive, causing patches to fall off and contaminate the tank water.

Long-Term Risks: What the Research Says (And Doesn't Say)

Here's where we have to be honest about the limits of current research. Float therapy has been studied since the 1950s (John C. Lilly's original sensory deprivation research), but the quality and scale of modern clinical studies is still catching up.

What We Know

The existing body of research — including a 2023 systematic review published in Frontiers in Psychology that analyzed 14 randomized controlled trials — found no evidence of serious long-term adverse effects from regular float therapy. Participants in these studies floated anywhere from once to three times per week over periods ranging from 4 to 12 weeks.

A notable study from Karlstad University in Sweden tracked 65 participants with stress-related pain over 12 sessions. They found sustained reductions in pain, anxiety, and depression with no reported long-term negative effects at a 4-month follow-up.

The LIBR research group has conducted some of the most rigorous float therapy research to date. Their published data, spanning several hundred participants, reports no serious adverse events.

What We Don't Know

Long-term effects of chronic, high-frequency floating. Most studies look at 8-12 sessions over a few months. We don't have strong data on what happens when someone floats 2-3 times per week for years. Anecdotal reports from experienced floaters are positive, but anecdotes aren't data.

Cumulative magnesium exposure. Transdermal magnesium absorption from Epsom salt is real but poorly quantified. A 2017 study found that bathing in Epsom salt solutions did raise blood magnesium levels, but the clinical significance for regular floaters is unclear. For people with healthy kidneys, this is likely a non-issue. For people with even mild kidney impairment, the long-term cumulative effect is genuinely unknown.

Neuroplastic effects of repeated sensory deprivation. The brain adapts to repeated experiences. Does regular floating change the brain's baseline sensitivity to stimulation? There's theoretical reason to think it might — but no longitudinal neuroimaging studies have been conducted to answer this question.

Interactions with ongoing mental health treatment. Float therapy is increasingly used alongside psychotherapy, EMDR, and other mental health modalities. The interaction effects are promising but under-studied.

The Bottom Line on Long-Term Safety

The absence of evidence isn't evidence of absence — but it's also not evidence of harm. Given that float therapy has been practiced for 70+ years with no documented pattern of long-term adverse effects, the risk profile appears genuinely low. Regular floating (1-2 times per month) is almost certainly safe for healthy adults. More frequent floating (weekly or more) is probably safe too, but the evidence base is thinner.

How to Minimize Your Risk: Practical Pre-Float Preparation

Preparation eliminates most side effects. Here's a checklist based on what experienced floaters and float center staff recommend.

Before Your Float

Don't shave or wax within 12 hours. Freshly exposed skin plus concentrated salt equals unnecessary stinging.
Eat a light meal 60-90 minutes before. Floating on an empty stomach can cause nausea. Floating on a full stomach can cause discomfort. A light snack is the sweet spot.
Skip the caffeine. Coffee within 2-3 hours of your float will fight the relaxation response and can increase anxiety in the tank. Some floaters report that caffeine-related jitters are amplified in the absence of other stimulation.
Apply petroleum jelly to any cuts, scrapes, or abrasions. Even small ones. Your cuticles, too, if they're cracked. Most centers provide this, but bringing your own ensures you don't miss any spots.
Remove contact lenses. If salt water gets in your eyes with contacts in, it's significantly more painful and harder to rinse out.
Use the bathroom immediately before. You don't want to cut your session short because you need to get out.
Don't apply lotions, oils, or heavy products. They'll come off in the water and affect water quality. Shower thoroughly before entering (all float centers require a pre-float shower).

During Your Float

Start with the light on if you're nervous. Every modern float tank has an interior light. Use it until you feel comfortable, then turn it off.
Leave the door/lid cracked if enclosed spaces bother you. You lose some of the sensory deprivation benefit, but you keep your sanity. That's a good trade.
Try a neck pillow if neck tension is an issue. The Epsom salt supports your body, but some people hold tension in their neck and find it difficult to let their head fully rest on the water. Most centers provide inflatable neck pillows.
If salt gets in your eyes, don't panic. There's a spray bottle of fresh water inside every properly equipped tank. Slowly wipe your eye with the back of your hand first, then spray with fresh water. Don't rub — that pushes salt further in.
Breathe. Seriously. Slow, deep breaths in the first few minutes set the tone for the entire session. If you feel anxious, focus on a 4-7-8 breathing pattern (inhale for 4 counts, hold for 7, exhale for 8).

After Your Float

Rise slowly. Sit up first. Wait 30 seconds. Stand slowly, holding the edge of the tank. The combination of low blood pressure and disorientation can cause dizziness if you jump up too fast.
Shower thoroughly. Rinse all the salt off, especially from your hair. If you leave it, your skin will feel dry and itchy within a few hours, and your hair will become stiff and brittle.
Hydrate. Drink water before and after. The osmotic effect of the salt solution can be mildly dehydrating.
Don't rush. Sit in the post-float area for 10-15 minutes. Have the tea they offer. Let your senses readjust before driving or doing anything that requires sharp focus.

Frequently Asked Questions

Can you drown in a float tank? The risk is extremely low. The high salt concentration creates buoyancy similar to the Dead Sea — your body floats effortlessly, and it's virtually impossible to turn face-down. You would have to actively work to submerge your face. That said, drowning risk exists for anyone who could lose consciousness unexpectedly (uncontrolled epilepsy, heavy sedation, extreme intoxication). Float centers should and do screen for these conditions. Never float under the influence of alcohol, recreational drugs, or heavy sedatives.

Is it safe to float while pregnant? Many women float safely during pregnancy, particularly in the second and third trimesters. The buoyancy provides significant relief from the physical discomforts of pregnancy. The water temperature (93.5°F) is below the threshold associated with birth defects. However, no large clinical trials have studied float therapy specifically in pregnant populations, so the "consult your OB-GYN first" advice is genuinely warranted here — not just a legal disclaimer.

Can float tanks cause ear infections? Salt water sitting in the ear canal for 60-90 minutes can create conditions favorable to bacterial growth, particularly if you have a history of swimmer's ear. Using the silicone earplugs provided by the center — or bringing your own — reduces this risk significantly. After floating, tilt your head to each side and gently pull your earlobe to drain any residual water. Some regular floaters use a few drops of rubbing alcohol or a 50/50 white vinegar and rubbing alcohol solution after floating to dry out the ear canal.

Are there any long-term side effects of regular floating? No long-term adverse effects have been documented in the clinical literature. Studies tracking participants over 4-12 months of regular floating found sustained benefits with no emerging negative effects. However, truly long-term data (years of regular use) is limited to observational reports from experienced floaters, which are overwhelmingly positive but not scientifically rigorous.

Should I float if I have anxiety or PTSD? Research from the Laureate Institute for Brain Research suggests float therapy can significantly reduce anxiety symptoms — but the first session may initially increase anxiety before providing relief. If you have severe anxiety or PTSD, consider: (1) choosing an open float pool rather than an enclosed pod, (2) keeping the interior light on for your first session, (3) starting with a shorter session (30 minutes), and (4) discussing float therapy with your mental health provider beforehand. Many therapists are now incorporating float therapy into treatment plans for anxiety and PTSD.

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