A handful of simple, inexpensive ingredients can turn an ordinary bath into a skin-softening treatment. Colloidal oatmeal, oils, milk, baking soda, and glycerin all work through different mechanisms to hydrate, exfoliate, or protect dry skin. What you add matters less than getting the basics right: lukewarm water, a soak of 5 to 10 minutes, and moisturizer applied immediately after while your skin is still damp.
Colloidal Oatmeal
Colloidal oatmeal is finely ground oat grain that dissolves into bathwater, leaving a milky, slightly slippery feel. It’s one of the most well-studied bath additives for dry, itchy skin. The active compounds, called avenanthramides, reduce inflammation by blocking the release of histamine from skin cells and suppressing the chemical signals that trigger redness and irritation. In lab and skin studies, avenanthramides significantly reduced both itch and the inflammatory response that makes dry skin feel hot or reactive.
You can buy colloidal oatmeal packets (Aveeno is the most common brand) or make your own by blending plain, unflavored oats in a food processor until they form a fine powder that turns water cloudy when stirred in. About one cup per bath is a standard amount. The water should look milky, not chunky. Colloidal oatmeal is gentle enough for sensitive and eczema-prone skin, which is why dermatologists recommend it so frequently.
Oils: Coconut, Sunflower, and Mineral
Adding a tablespoon or two of oil to your bath creates a thin layer on the skin’s surface that slows moisture loss after you get out. A clinical trial comparing coconut oil and mineral oil as moisturizers for mild to moderate dry skin found them equally effective. Both significantly improved skin hydration and increased surface lipid levels without disrupting the skin barrier or altering skin pH. Patients in that study showed a slight subjective preference for coconut oil, though the difference wasn’t statistically significant.
Sunflower seed oil is another good option because it’s rich in linoleic acid, a fatty acid the skin uses to maintain its barrier. Olive oil, on the other hand, can actually worsen barrier function in some people, so it’s not the best choice for very dry or eczema-prone skin. Whichever oil you use, be careful getting in and out of the tub since oil makes surfaces slippery.
Milk
Milk baths aren’t just a beauty myth. Milk naturally contains lactic acid, an alpha hydroxy acid that dissolves the bonds holding dead skin cells together. This gentle exfoliation removes the rough, flaky layer that makes dry skin feel sandpapery, leaving smoother skin underneath. Goat’s milk has higher concentrations of lactic acid than cow’s milk, so it provides more exfoliation. One to two cups of whole milk (or full-fat powdered milk) per bath is enough. The fat in the milk also provides a mild moisturizing effect.
Baking Soda
The National Eczema Association recommends adding a quarter cup of baking soda to a lukewarm bath for itch relief. Baking soda has mild anti-inflammatory properties and helps balance the pH of bathwater, which can soothe reactive, irritated skin. The protocol is straightforward: add 1/4 cup to your bath, soak for 15 to 20 minutes, rinse with cool water afterward, and follow with a fragrance-free moisturizer. Baking soda won’t deeply hydrate on its own, but it’s useful when dryness comes with persistent itching.
Glycerin
Glycerin is a humectant, meaning it pulls water from the environment into your skin rather than just sitting on top of it. Adding a few tablespoons of vegetable glycerin to bathwater can boost hydration and support barrier function. It works especially well when paired with an oil or a rich moisturizer afterward, because the humectant draws moisture in while the oil or cream seals it there. Vegetable glycerin is inexpensive and available at most pharmacies. It dissolves easily in warm water.
Epsom Salt: Worth the Caution
Epsom salt (magnesium sulfate) baths are popular, but the evidence for skin hydration is thin. Studies on Dead Sea salt baths have shown improved skin barrier function and hydration, likely due to their magnesium content. No equivalent research exists specifically for Epsom salt. It can help soften rough skin and remove scales, but soaking too long may actually irritate dry skin further. If you try it, two cups in a warm bath for no more than 15 minutes is the general recommendation. Follow with moisturizer immediately.
What to Skip or Use Carefully
Essential oils are the biggest pitfall. Roughly 80 essential oils have been shown to cause contact allergic reactions, and the most common offenders are some of the most popular: lavender, tea tree, peppermint, and ylang-ylang. Lavender oil contains linalool and linalyl acetate, both known allergens. Tea tree oil breaks down when exposed to air, producing peroxides and other strong sensitizers. Peppermint oil contains menthol and several other allergenic compounds. If your skin is already dry and compromised, adding these oils to a bath increases your risk of irritation or allergic contact dermatitis.
Citrus-based oils, including bergamot, carry an additional risk. They contain compounds called furocoumarins that react with UV light, potentially causing a phototoxic skin reaction if you go outside after your bath. If you want fragrance, a few drops of oil mixed into a carrier oil (like coconut or sunflower) is safer than dropping essential oils directly into water, where they float undiluted on the surface and contact your skin at full strength.
Apple Cider Vinegar
Apple cider vinegar baths are sometimes recommended for restoring the skin’s natural acidity, which tends to be disrupted in dry or eczema-prone skin. The dilution matters. Research protocols have used a 0.5% acetic acid concentration, which works out to roughly 2.4 cups of apple cider vinegar in a large basin of water (about 21.6 cups). For a full bathtub, you’d use about two cups in a standard tub. Start with less if you’ve never tried it, and stop if you notice stinging or redness. The evidence for major skin improvement is limited, but some people find it helps with itch.
How You Bathe Matters as Much as What You Add
The temperature of your bathwater and what you do afterward can make or break any additive’s benefits. Hot water strips oils from the skin and worsens dryness. Lukewarm is the target. Most dermatology guidelines recommend keeping baths to 5 to 10 minutes for dry or eczema-prone skin.
The single most important step is what dermatologists call “soak and smear.” When you get out of the bath, don’t towel off completely. Pat your skin lightly so it stays damp, then immediately apply a thick moisturizer or ointment. This traps the water your skin absorbed during the bath and prevents it from evaporating. Waiting even a few minutes allows that moisture to escape. The moisturizer you choose matters too: ointments and creams outperform lotions for dry skin because they contain more oil and less water. Fragrance-free options are least likely to cause irritation.