You can make a basic onion extract at home by simmering diced onion in a carrier oil or water, then straining and applying the liquid to scars. But before you start, it helps to understand what onion extract actually does for scars and what kind of results are realistic, because the clinical evidence is more modest than most people expect.
What Onion Extract Does to Scar Tissue
Onions contain compounds, particularly a flavonoid called quercetin, that appear to slow the overproduction of collagen in healing skin. Scars form when your body lays down collagen fibers in a dense, disorganized pattern. Onion extract seems to calm that process, which can reduce how much a scar rises above the surrounding skin.
In a clinical trial on surgical scars, the side treated with 12% onion extract gel three times daily showed measurably lower scar height by week 4 compared to the untreated side, and the difference held through week 12, with over 56% of patients showing reduced scar height on the treated side. However, there was no statistically significant difference in scar redness, scar flexibility, or overall cosmetic appearance between treated and untreated sides. Most scars in the study were rated as showing “no improvement” in overall cosmesis at 12 weeks, on both sides. So the effect is real but limited: onion extract may flatten a raised scar somewhat, but it’s unlikely to transform its color or texture dramatically.
How Commercial Products Compare
The most widely known commercial product, Mederma, contains 10% aqueous onion extract as its active ingredient. Clinical formulations typically use either 10% or 12% concentrations. The 12% version is standard for adults, while 10% is more common in products designed for children. These products use a standardized extraction process to ensure consistent concentration, something that’s difficult to replicate in a kitchen. A homemade extract will have an unknown concentration, which means results may be weaker or more variable than what clinical trials measure.
Simple Homemade Onion Extract Methods
Water-Based Extract
Peel and finely dice one medium white or yellow onion. Place the pieces in a small saucepan with just enough distilled water to cover them, roughly one cup. Bring to a gentle simmer, not a rolling boil, and let it cook for 15 to 20 minutes until the liquid reduces by about half and turns slightly golden. Remove from heat, let it cool completely, then strain through a fine mesh sieve or cheesecloth into a clean glass jar. Press the onion pieces to extract as much liquid as possible. Store in the refrigerator and use within 5 to 7 days.
Oil-Based Extract
An oil-based version absorbs into skin more easily and has a longer shelf life. Dice one medium onion and place it in a small saucepan with about half a cup of a light carrier oil like coconut oil, olive oil, or jojoba oil. Heat on the lowest setting for 30 to 45 minutes. You want the onion to gently infuse into the oil without frying or browning. Strain into a clean glass container and store in a cool, dark place. This version keeps for two to three weeks.
Raw Juice Method
The simplest approach is to grate a fresh onion on a fine grater or blend it, then squeeze the pulp through cheesecloth to collect the raw juice. This gives you the most concentrated version, but it’s also the most likely to irritate your skin because the raw compounds haven’t been softened by heat. It must be refrigerated and used within a few days.
How to Apply It
Before putting any homemade extract on a scar, test it first. Apply a small amount to the inside of your forearm and wait 24 hours. If you see redness, itching, or a rash, the extract is too strong or your skin is sensitive to it. You can try diluting it further with water or carrier oil.
If the patch test goes well, apply a thin layer directly to the scar two to three times per day. Clinical studies used this three-times-daily frequency with a 12% formulation, so consistency matters more than quantity. Gently massage the extract into the scar for 30 to 60 seconds each time to help absorption. Cover with a bandage if the area rubs against clothing.
Start application once the wound has fully closed and any scabs have fallen off naturally. Applying any extract to an open wound risks irritation and infection. The earlier you begin after the wound closes, the better your chances of influencing collagen production while the scar is still actively forming. Plan to continue for at least 8 to 12 weeks before evaluating results, since meaningful changes in scar height took that long to appear in clinical settings.
Limitations of a DIY Approach
The biggest challenge with homemade onion extract is that you have no way to measure the actual concentration of active compounds in your preparation. Commercial gels are formulated to deliver a consistent 10% to 12% dose with each application. Your kitchen extract could be significantly weaker or, with the raw juice method, potentially stronger and more irritating.
Homemade extracts also lack the gel base that helps commercial products stay on the skin and absorb evenly. Water-based extracts in particular will run off the scar quickly. You can thicken your extract by mixing it with pure aloe vera gel at roughly a 1:1 ratio, which also adds its own mild skin-soothing properties and helps the liquid stay in place.
Even in clinical trials using standardized formulations, onion extract primarily reduced scar height. It did not significantly improve redness or overall cosmetic appearance over 12 weeks. For older, mature scars that have already finished the remodeling process, the effect is likely even smaller. Onion extract works best on new scars that are still actively forming, particularly raised or hypertrophic scars. Flat, discolored scars or depressed acne scars involve different tissue changes and are unlikely to respond to this treatment.
Getting Better Results
If you’re committed to the DIY route, a few adjustments can help. Use fresh onions rather than ones that have been sitting in your pantry for weeks, since quercetin and other active compounds degrade over time. Yellow onions tend to have higher quercetin content than white or red varieties. Make small batches frequently rather than one large batch, since the active compounds break down in storage even when refrigerated.
Combining onion extract with silicone sheeting or silicone gel, which has its own strong evidence base for scar management, may produce better results than either approach alone. Apply the onion extract, let it dry, then place a silicone sheet over the scar. Keeping the scar moisturized and protected from UV exposure also supports better healing outcomes, since sun exposure can permanently darken new scar tissue.