You can make rosemary oil at home by steeping dried rosemary in a carrier oil for two to four weeks (cold infusion) or by gently heating the mixture for one to two hours (hot infusion). Both methods pull the plant’s beneficial compounds into the oil, giving you a fragrant product useful for hair care, skin, or cooking. The method you choose depends on how much time you have and how potent you want the final product.
There’s also a third option, steam distillation, which produces a concentrated essential oil rather than an infused oil. Each approach requires different equipment and yields a different product, so it helps to know exactly what you’re after before you start.
Infused Oil vs. Essential Oil
Most people searching for “rosemary oil” actually want an infused oil: rosemary steeped in olive oil, jojoba oil, or another carrier. This is the simplest method, requires no special equipment, and produces a mild, ready-to-use oil you can apply directly to your scalp or skin, or drizzle over food.
Essential oil is a different product entirely. It’s a highly concentrated liquid extracted through steam distillation, and even a large batch of rosemary yields only a tiny amount. You’d need a two-vessel distiller, where one vessel boils water to generate steam and a second vessel holds the rosemary. As steam passes through the plant material, it breaks down cell structures and carries volatile compounds upward. After the vapor condenses, the essential oil floats on top of the water (called a hydrosol) and is separated using a funnel. It’s a rewarding project if you have the equipment, but for most home uses, an infused oil is more practical.
Cold Infusion: The Slow Method
Cold infusion is the gentlest approach and preserves the widest range of rosemary’s heat-sensitive compounds. The tradeoff is patience: you’ll wait two to four weeks for a finished product.
Start by dehydrating your rosemary. This step is critical for safety (more on that below). Chop the sprigs to fit your jar, wash them, then spread them on a parchment-lined baking sheet. Set your oven to its lowest temperature and leave the rosemary inside for one to two hours, until the stems snap cleanly rather than bend. No moisture should remain.
Once the rosemary is fully dried, pack it loosely into a clean glass jar and pour your carrier oil over it until the herbs are completely submerged. Olive oil is the most common choice, but jojoba and sweet almond oil also work well, especially for hair and skin applications. Seal the jar tightly and place it in a cool, dark spot. Give it a gentle shake every few days. After two to four weeks, strain the oil through cheesecloth or a fine mesh sieve into a clean bottle, pressing out as much liquid as you can. Discard the spent herbs.
Hot Infusion: Ready in Hours
If you don’t want to wait weeks, a hot infusion can be ready in one to two hours. The heat speeds up the transfer of rosemary’s compounds into the oil, though there is some risk of overheating, which can degrade beneficial antioxidants. Key compounds in rosemary, like its primary antioxidants, begin to break down above roughly 175°F (80°C), so low and slow is the goal.
Use the same dried rosemary preparation described above. Combine the herbs and carrier oil in a saucepan or double boiler over the lowest heat setting your stove allows. A double boiler is preferable because it keeps the temperature more stable and reduces the chance of scorching. Let the mixture warm gently for one to two hours, stirring occasionally. The oil should never simmer or bubble. If you see any wisps of smoke, it’s too hot.
After heating, let the oil cool completely, then strain it through cheesecloth into your storage container.
Why Drying the Rosemary Matters
Fresh rosemary contains moisture, and moisture trapped inside oil creates an oxygen-free environment where Clostridium botulinum spores can grow. These spores produce the botulism toxin, which causes serious illness. This isn’t a theoretical risk. Penn State Extension specifically warns that herbs used to flavor oils are low-acid foods and a known source of these spores.
Using thoroughly dried rosemary eliminates most of the water content and dramatically lowers this risk. Never let any water get into your infusion at any stage, whether from wet utensils, condensation, or improperly dried herbs.
If you do want to use fresh rosemary, there’s a tested protocol developed by University of Idaho researchers. Soak the rosemary stems (leaves still attached) in a 3 percent citric acid solution for at least 24 hours before adding them to oil. Make the solution by stirring 1 tablespoon of citric acid into 2 cups of water, then use a ratio of about 1.7 ounces of herbs to 2 cups of solution. Keep the herbs fully submerged with a weight. Shorter soaking times or weaker solutions won’t adequately acidify the plant material and can result in an unsafe product. Once you drain the citric acid and add the herbs to oil, never toss in additional fresh sprigs later, since those won’t be acidified.
Storage and Shelf Life
Store your finished rosemary oil in a dark glass bottle (amber or cobalt blue) to limit light exposure, which accelerates oxidation and breaks down the oil’s active compounds over time. Keep it in a cool, dark cabinet or in the refrigerator.
Shelf life depends on how you made it and what herbs you used. Oil infused with properly dried rosemary and stored in the refrigerator keeps for up to three months. If you used fresh rosemary (even with the citric acid treatment), use the oil within two to four days and keep it refrigerated the entire time. Label your bottle with the date you made it so you don’t have to guess later.
Choosing a Carrier Oil
Your carrier oil affects both the shelf life and the final use of the product. Olive oil is a solid all-purpose choice: it’s inexpensive, widely available, and works for both culinary and topical uses. For hair care, many people prefer jojoba oil because its structure closely resembles the natural oils your scalp produces, so it absorbs without feeling greasy. Sweet almond oil and coconut oil are other popular options for skin and hair applications. If you plan to cook with your rosemary oil, stick with olive oil, avocado oil, or another food-grade option.
Whichever oil you pick, make sure it’s fresh. Rancid carrier oil will produce a rancid end product no matter how good your rosemary is. Smell the oil before you start. It should be neutral or pleasant, with no sharp or stale odor.
What Rosemary Oil Is Used For
Rosemary-infused oil has a long history in cooking, but it’s gained serious attention for hair growth in recent years. A 2015 randomized trial published in SKINmed Journal assigned 100 people with androgenetic alopecia (pattern hair loss) to use either rosemary oil or 2% minoxidil for six months. At the three-month mark, neither group showed significant improvement. By six months, both groups had a significant increase in hair count compared to baseline, and there was no statistical difference between the two treatments. The takeaway: rosemary oil matched minoxidil for hair regrowth over six months, but it takes time to work. Don’t expect visible changes before the three-month mark.
Topically, rosemary oil is also used for scalp massage, muscle soreness, and as a fragrant addition to homemade lotions or bath products. For any skin application, do a small patch test on the inside of your wrist before applying it more broadly, especially if you have sensitive skin.