Several groups of people should avoid soaking in Epsom salt, including those with kidney disease, diabetes-related nerve damage, open wounds, skin infections, and certain heart conditions. While Epsom salt baths are generally low-risk for healthy adults, the magnesium sulfate in the salt can cause real problems for people whose bodies can’t process it normally or whose skin is already compromised.
People With Kidney Disease
Your kidneys are responsible for filtering excess magnesium out of your blood. When they aren’t working well, magnesium can build up to dangerous levels, a condition called hypermagnesemia. The Mayo Clinic specifically notes that magnesium sulfate should be used with caution in people with kidney disease because the effects may be increased due to slower removal from the body.
Even through the skin, some magnesium does cross into the bloodstream during a soak. A small study at the University of Birmingham found that after seven days of 12-minute Epsom salt baths, most participants showed rising blood magnesium levels and significantly higher magnesium in their urine, indicating the mineral had entered their systems and their kidneys were working to clear it. For someone with healthy kidneys, that’s no issue. For someone with impaired kidney function, that extra magnesium has nowhere to go.
Mild magnesium buildup causes nausea, flushing, lightheadedness, and low blood pressure. At higher levels, it can interfere with heart rhythm and breathing. In rare but documented cases, magnesium overload from Epsom salt (ingested, not soaked in) has been fatal, even in people with normal kidney function. If you have chronic kidney disease at any stage, talk with your nephrologist before using Epsom salt baths.
People With Diabetes or Nerve Damage
Diabetes creates a specific combination of risks that makes soaking dangerous. Nerve damage, which affects a large percentage of people with diabetes over time, reduces your ability to feel heat and pain. That means you may not notice when bath water is too hot, raising the risk of burns. The Cleveland Clinic flags this as a direct concern with foot soaks in particular.
Poor circulation, another common complication of diabetes, slows healing. A minor burn or skin crack from soaking can become a serious wound that takes weeks to close. Epsom salt also draws moisture from skin, which can worsen the dry, cracked feet many people with diabetes already deal with. On top of that, diabetes increases susceptibility to fungal infections, and prolonged soaking in warm water creates exactly the kind of environment fungi thrive in.
People With Open Wounds, Burns, or Skin Infections
The Cleveland Clinic lists several skin-related conditions that rule out Epsom salt baths:
- Open wounds: Salt in an open wound isn’t just painful. It can irritate tissue and delay healing.
- Severe burns: Damaged skin has lost its barrier function, meaning far more magnesium can be absorbed and the salt itself can aggravate the injury.
- Skin infections: Soaking can spread bacteria across a larger area of skin or deeper into tissue.
- Severe skin inflammation: Conditions like a bad eczema flare or contact dermatitis can worsen with salt exposure.
If you have minor, intact skin irritation, a brief soak may be fine. But anything involving broken skin, active infection, or significant inflammation is a reason to skip it.
People With Low Blood Pressure or Heart Conditions
Hot water dilates blood vessels and temporarily drops blood pressure. For most people, this feels relaxing. For someone who already runs low on blood pressure, it can cause dizziness, fainting, or falls, especially when standing up after a bath. Healthline specifically flags low blood pressure as a reason to check with your doctor before soaking.
Excess magnesium also affects heart rhythm. While this is primarily a concern with oral or intravenous magnesium rather than what’s absorbed through skin, the combination of hot water and magnesium exposure may be worth avoiding if you have an irregular heartbeat or take medications that affect your heart rate or blood pressure. The effects compound: the heat lowers blood pressure while the magnesium can further slow the heart.
Pregnant Women Need Temperature Limits
Pregnancy doesn’t rule out Epsom salt baths entirely, but it does impose strict conditions. The Cleveland Clinic’s obstetric guidance is clear: bath water should stay at or below 99°F (37°C). In the first trimester, water hotter than that raises your core body temperature and increases the risk of neural tube defects like spina bifida, because that’s when the brain and spinal cord are forming.
The temperature restriction doesn’t lift after the first trimester. Later in pregnancy, your blood vessels are carrying significantly more blood to supply the placenta. Hot water drops your blood pressure further, meaning it takes longer for blood to reach your head. Standing up from a hot bath can cause lightheadedness or fainting, and the risk of a dangerous fall increases as your belly grows. Hot tubs, saunas, and steam rooms are off-limits for the same reason.
Fragrance-free Epsom salts in a warm (not hot) bath are generally considered safe during pregnancy and can help with the aches of the third trimester. The key variable isn’t the salt; it’s the water temperature.
People With a Magnesium Sulfate Allergy
True allergic reactions to magnesium sulfate are rare but documented. Case reports describe patients developing itchy hives on the face, arms, neck, and chest, along with flushed skin and shortness of breath. In more severe cases, reactions included a swollen tongue, rapid breathing, and drops in oxygen levels requiring emergency treatment. Most of these cases involved intravenous magnesium sulfate rather than baths, but if you’ve ever had a reaction to magnesium sulfate in any form, avoid soaking in it.
A milder version of this is simple skin sensitivity. Some people develop redness, itching, or a rash after an Epsom salt bath without it being a full allergic reaction. If your skin consistently reacts to Epsom salt, there’s no reason to push through it.
Children and Infants
There are no well-established guidelines for Epsom salt baths in young children. Research on magnesium sulfate baths in pediatric populations is limited, and existing studies note that more data is needed before recommending salt baths as therapy for children’s skin conditions. Children have a higher skin surface area relative to their body weight, which could mean proportionally greater absorption. Their kidneys are also still maturing, particularly in infants, making them less efficient at clearing excess magnesium. If you’re considering an Epsom salt bath for a child, use a lower concentration and keep the soak brief.
Safe Use for Everyone Else
If none of the above applies to you, Epsom salt baths are straightforward. Use 1 to 2 cups in a standard bathtub of warm water and soak for about 15 minutes. Longer isn’t necessarily better, as extended soaking dries out skin. For a localized soak or compress, dissolve 1 cup in a quart of warm water and apply for 15 to 30 minutes.
It’s worth noting that the science on whether magnesium actually absorbs through skin in meaningful amounts is contested. A review published in the journal Nutrients concluded that the promotion of transdermal magnesium absorption is “scientifically unsupported,” pointing out that magnesium ions are too large to easily pass through the skin’s outer layer. The small Birmingham study did find modest blood level increases, but the review’s authors questioned the study’s methodology. So while Epsom salt baths may feel good and help with muscle soreness through the warm water itself, the magnesium absorption claims remain unproven.