Plain soap is already antibacterial. The surfactants in any soap, whether store-bought or homemade, physically destroy bacteria by pulling apart the fatty outer membranes that hold them together. The CDC states that studies have not found any added health benefit from using antibacterial soap over plain soap for everyday consumer use. So if you’re making soap at home, you’re already making something that kills bacteria effectively. That said, there are ways to boost your homemade soap with natural antimicrobial ingredients if that’s your goal.
Why Regular Soap Already Works
Soap molecules have a split personality: one end attracts water, and the other end attracts fat. Bacterial cell membranes are made of a fatty double layer, and when soap meets that layer, its fat-loving end wedges itself between the membrane’s molecules. This disrupts the cohesive energy holding the membrane together, essentially tearing holes in the bacterium’s outer wall. The cell loses its structural integrity and dies. This same mechanism works against enveloped viruses like the flu and coronaviruses.
This is a physical process, not a chemical one. It doesn’t require any special “antibacterial” additive. It happens every time you lather up and scrub for 20 seconds. The scrubbing action lifts bacteria from your skin, the soap destroys their membranes, and the rinse water carries everything away.
What Happened to Antibacterial Soap Ingredients
In 2016, the FDA banned 19 active ingredients, including triclosan and triclocarban, from consumer antiseptic wash products. The reason was straightforward: manufacturers couldn’t demonstrate that these chemicals were more effective than plain soap and water at preventing illness, or that they were safe for daily long-term use. Some research has also suggested that antibacterial soap use may contribute to antibiotic resistance.
A handful of ingredients, including benzalkonium chloride, benzethonium chloride, and chloroxylenol, were not included in the ban but remain under review. These are used primarily in healthcare settings, not in typical home soapmaking.
A Basic Cold Process Soap Recipe
Cold process soapmaking uses a chemical reaction called saponification, where a strong alkali (lye) reacts with fats or oils to produce soap. This is the foundation for any bar soap, antibacterial or otherwise. You’ll need a digital kitchen scale, a stick blender, a soap mold, safety goggles, and chemical-resistant gloves.
A simple beginner recipe uses roughly 16 oz of olive oil, 6 oz of coconut oil, and 4 oz of a harder fat like shea butter. The exact amount of lye (sodium hydroxide) you need depends on the specific oils you choose, because each fat requires a different amount of lye to fully convert into soap. Use an online lye calculator to get the precise measurement for your recipe. Never eyeball it.
Most soapmakers use a 5% “superfat” setting in their calculator, which means the formula intentionally includes slightly more oil than the lye can convert. This builds in a safety margin so no unreacted lye remains in the finished bar, and the leftover oil makes the soap gentler on skin. A 0% superfat leaves no room for measurement error and can produce a harsh, irritating bar.
The Process
- Prepare the lye solution. Slowly add lye to cold distilled water (never the reverse) in a well-ventilated area. The mixture will heat up to around 200°F and release fumes. Stir until dissolved, then set aside to cool.
- Melt and combine your oils. Heat the solid fats until liquid, then mix with your room-temperature liquid oils.
- Combine at similar temperatures. When both the lye solution and oil mixture are around 100-110°F, pour the lye solution into the oils.
- Blend to trace. Use a stick blender until the mixture thickens to a pudding-like consistency. This is when you add any essential oils or other extras.
- Pour and cure. Pour into molds, insulate with a towel, and let sit 24-48 hours before unmolding. Then cure the bars on a rack for 4-6 weeks, turning occasionally. This waiting period allows excess water to evaporate and saponification to fully complete.
Adding Natural Antimicrobial Ingredients
If you want to go beyond what plain soap already does, certain essential oils have well-documented antimicrobial properties. Tea tree oil is the most studied. Research shows it inhibits the growth of Staphylococcus aureus at concentrations between 0.5% and 1.25%, and kills it at 1-2%. A handwash study found that a 5% tea tree oil solution in water performed significantly better than plain soft soap at reducing bacteria on volunteers’ hands.
For a cold process bar, adding tea tree oil at roughly 2-3% of your total oil weight gives you a meaningful concentration after curing. For a batch using 26 oz of base oils, that works out to about 0.5-0.8 oz of tea tree oil, added at trace.
Cinnamon essential oil is another potent option, with lab studies showing it inhibits bacterial growth at very low concentrations (a median of 0.5 mg/ml across multiple bacterial species). It can be irritating to skin at higher concentrations, though, so keep it below 0.5% of total oil weight and always do a skin patch test with your finished bar. Oregano oil also has antimicrobial properties but requires much higher concentrations to be effective, making it less practical for soap.
Essential oils lose some potency during saponification because of the high pH environment. Adding them at a light trace (when the batter is just barely thickened) rather than a heavy trace minimizes heat exposure and preserves more of their active compounds.
Making Liquid Antibacterial Soap
Liquid soap uses potassium hydroxide instead of sodium hydroxide as its alkali. The process is similar but takes longer, requiring you to cook the soap paste in a slow cooker or double boiler for several hours until it’s fully saponified, then dilute the paste with distilled water until it reaches your desired consistency.
The critical difference with liquid soap is that you’re creating a water-based product, which means bacteria and mold can grow in it over time. Bar soap’s low water content and high pH make preservation a non-issue, but liquid soap needs a preservative. The finished soap’s pH typically falls between 8 and 10, which limits your preservative options. You can add your antimicrobial essential oils (tea tree at about 1-2% of the total finished weight) which serve double duty as fragrance and preservation support, but a broad-spectrum preservative designed for the alkaline pH range adds an extra layer of protection for shelf stability.
What Antibacterial Soap Can and Cannot Do
Even with essential oils added, homemade soap is not a medical-grade antiseptic. It won’t sterilize a wound or replace proper disinfection protocols. What it will do is clean your hands effectively, the same way any well-made soap does, with the added benefit of natural compounds that have genuine antimicrobial activity in lab settings.
Research on antibacterial soap’s effects on skin bacteria tells an interesting story. A study in rural Madagascar found that using antibacterial soap (containing triclocarban) didn’t reduce the overall number of bacterial species living on participants’ skin. What it did change was the composition of those communities, shifting which species were present. Those shifts persisted for at least two weeks after the study ended. Your skin hosts a complex ecosystem of beneficial microbes that help protect against pathogens, regulate inflammation, and maintain your skin’s barrier function. Aggressively trying to eliminate bacteria from your skin can disrupt that balance without providing a clear health benefit.
The most effective thing you can do for hand hygiene is simple: wash with any soap, scrub all surfaces of your hands for at least 20 seconds, and rinse thoroughly. The mechanical action of washing matters more than what’s in the soap.