A baking soda bath raises the pH of your bathwater from mildly acidic (around 5.5) to near-neutral (around 7.9), creating a gentle alkaline soak that can calm itchy, irritated, or inflamed skin. It’s one of the oldest home remedies in dermatology, and there’s reasonable evidence behind several of its uses.
How It Works on Your Skin
Your skin’s outermost layer is naturally slightly acidic. This “acid mantle” is protective, but when skin is irritated, inflamed, or broken out, that acidity can contribute to stinging and discomfort. Dissolving baking soda (sodium bicarbonate) in bathwater neutralizes some of that acidity, both in the water itself and on the skin’s surface. Two handfuls in a half-filled tub is enough to shift the pH from about 5.5 to 7.9.
This shift does a few things at once. It softens the water, which helps loosen dry, scaly skin. It creates an environment that’s less hospitable to certain fungi and bacteria. And for many people, it simply feels soothing on raw, itchy patches in a way that plain water doesn’t.
Relief for Psoriasis
The strongest evidence for baking soda baths comes from psoriasis research. In a study of 31 people with mild to moderate psoriasis, soaking in baking soda baths on alternating days for three weeks produced significant improvement. About 10% of participants saw near-complete clearing (an 87% reduction in their psoriasis severity score), another 21% saw roughly 61% improvement, and the rest experienced moderate relief. On average, severity scores dropped by about 39%. Participants also reported less itching and irritation compared to the control group.
The concentration used in that study was about 3.5 to 6 grams of baking soda per liter of bathwater, which works out to roughly two-thirds to one cup per full tub. That range has been used safely and effectively across the available research. It’s worth noting that a separate study testing baking soda mixed into a cream (rather than dissolved in bathwater) found no benefit for psoriasis, suggesting the full-body soak matters.
Eczema and Itchy Skin
For eczema, the National Eczema Association recommends adding a quarter cup of baking soda to a warm bath to help relieve itching. The mechanism is similar: the alkaline water softens scales, soothes inflamed skin, and may reduce the sting that comes with raw, cracked patches.
Baking soda baths also show promise for a condition called aquagenic pruritus, where contact with water itself triggers intense itching. Observational reports found that adding as little as 25 grams of baking soda to bathwater provided relief for some patients, while others needed 100 to 200 grams. For general itchiness from things like chickenpox, Seattle Children’s Hospital recommends soaking in lukewarm water with about 2 ounces of baking soda.
Antifungal Effects
Lab research shows that baking soda slows the growth of Candida albicans, the fungus behind most yeast infections. At sufficient concentrations, it reduced the fungus’s normal growth rate by about 1.5 times, cut the formation of its invasive thread-like structures by 93%, and halved its ability to form the protective biofilms that make infections stubborn and recurring. The effect is fungistatic, meaning it stops the fungus from growing rather than killing it outright.
This doesn’t mean a baking soda bath will cure a yeast infection on its own, but it may help as a complement to standard treatment. The research also found that baking soda worked synergistically with common antifungal medications, making them more effective together than either alone.
How to Prepare a Baking Soda Bath
The amount you use depends on the purpose:
- General soothing soak: A quarter cup to 2 cups in a full warm bath
- Eczema relief: A quarter cup in warm (not hot) water
- Psoriasis: About two-thirds to 1 cup per tub, every other day for up to three weeks
- Diaper rash (infants): 2 tablespoons in a warm bath, soaking the affected area for 10 minutes, up to twice daily
- Chickenpox itching (children): About 2 ounces in lukewarm water
Stir the baking soda into the water until it dissolves fully before getting in. Use warm rather than hot water, since hot water strips oils from the skin and can worsen dryness and itching. For most purposes, 10 to 20 minutes of soaking is sufficient. Pat your skin dry afterward rather than rubbing, and follow up with a fragrance-free moisturizer to lock in hydration while your skin is still slightly damp.
Safety and Risks
For most people, a baking soda bath at reasonable concentrations is safe. The risks show up at the extremes: excessive amounts, prolonged use, or application to broken skin.
Case reports highlight what can go wrong. A 4-month-old infant who received excessive and prolonged baking soda application for diaper rash developed a dangerous electrolyte imbalance called metabolic alkalosis, where too much of the compound was absorbed through the skin. The condition resolved once the baking soda was stopped. Similar problems were reported in a 69-year-old woman applying it daily to a cancerous breast lesion and a 65-year-old man using it on an open foot ulcer while also taking it by mouth.
The pattern in these cases is the same: large amounts applied to damaged or broken skin over an extended period allowed too much sodium bicarbonate to absorb into the bloodstream. Intact skin is a much better barrier. Stick to the recommended concentrations, limit soaks to a reasonable duration, and avoid using baking soda baths on large open wounds or severely broken skin. For infants, use the lower amounts recommended for children and keep soaks brief.