Rosemary (Rosmarinus officinalis) is a small evergreen shrub that grows most heavily in Mediterranean countries such as Spain, Italy, Portugal, Southern France, Greece, North Africa, and areas of Turkey, Lebanon and Egypt. It grows in particular abundance by rocky limestone hillsides near the sea.
Rosemary is most famous as a culinary herb, particularly in Italian cuisine where it’s believed to compliment the taste of lamb extremely well. Rosemary herbs have been around for a long time; in Ancient Greece they revered the plant as they believed it could enhance and strengthen memory.
However what we’re interested in today is the powers of rosemary extract, specifically as a topical treatment used against acne. We’ve already discussed essential oils derived from herbs, such as thyme oil and tea tree oil, both of which reduce p.acnes bacteria very nicely.
Does rosemary extract, not to be confused with the anti-inflammatory rose water, which we’ve also covered, reduce acne when applied to the skin? According to an excellent study published in 2013, the answer is a very firm yes.
Study – rosemary calms inflammation from acne bacteria
Rosemary extract and rosemary oil already have tons of studies showing that they reduce the indirect conditions behind acne on the skin.
For instance, they both reduce inflammation, are known to kill a wide spectrum of bacteria, can hoover up reactive oxygen species, and can protect against UVB radiation (see below).
However, we now have a study showing that rosemary extract specifically inhibits propionibacterium acnes, or p.acnes, the classic acne bacteria that triggers an inflammatory response and leads to pimple formation.
A team of scientists from the Taipei Medical University in Taiwan set out to examine the effect of rosemary extract on p.acnes bacteria induced inflammation, both in vivo (on human subjects) and in vitro (on cells). First they measured the effect of rosemary extract on inflammation without the presence of p.acnes. Then they examined its powers in the presence of p.acnes, by measuring numerous pro-inflammatory chemicals behind acne such as TNF-a, interleukin-8, and interleukin-1beta.
Here’s what they found:
For the in vitro test, the main conclusion was that rosemary extract had no effect on TNF-a, IL-8, IL-1b, or other inflammatory chemicals when p.acnes was absent. But when p.acnes was present, rosemary extract “significantly suppressed” levels of all those chemicals.
That’s excellent news, as it provides direct evidence that rosemary extract can inhibit the specific inflammation behind acne.
Rosemary extract also reversed an increase in NF-kappaB, the “master molecule” of inflammation that gives birth to all the chemicals above. Even better, rosemary extract did not just reduce inflammatory chemicals; it reduced their production at the genetic level.
Rosemary extract could reduce the inflammation of cells exposed to p.acnes for both 8 hours and 16 hours. Most interesting was the compounds responsible; scientists identified rosmarinic acid, carnosol, and carnosic acid as the chief anti-inflammatory substances.
They all specialised in different inflammatory chemicals; rosmarinic acid significantly reduced interleukin-8 production, but had no effect on interleukin-1beta. Carnosol and carnosic acid, meanwhile, significantly inhibited IL-1β levels at the lower concentrations of 2.5 μM, and significantly increased IL-8 secretion at higher concentration, which is no problem, since the overall extract was shown to lower IL-8.
Luckily, the rosemary extract contained plenty of those medicinal compounds. According to the study, the contents of carnosol, carnosic acid, and rosmarinic acid the extract were 0.57, 1.98 and 0.43 mg per gram of dried leaves, respectively.
Even better is that none of the three compounds inhibited the pro-inflammatory chemical TNF-a. What makes that so great? The fact the entire rosemary extract was shown to reduce TNF-a substantially. It means that there’s almost certainly other potent acne-clearing compounds in rosemary extract that the scientists didn’t examine.
Later, in the discussion section of the paper, they speculated that two rosemary compounds called ursolic acid and luteolin, which are known to reduce TNF-a, could be responsible. They then mentioned how a “vast number” of phytochemicals have been identified in rosemary.
As for the in vivo study, scientist began by injecting mice ears with p.acnes in order to induce inflammation. The ears swelled up and reddened accordingly. Scientists then applied the rosemary extract, and observed both a reduction in ear thickness and swelling, and p.acnes induced inflammation of the ear.
The conclusion to the entire study was very promising: “in conclusion, the present results provide evidence that ERE reduces P. acnes–induced inflammation in vitro and in vivo”.
While they commented that “it is still obligatory to evaluate the safety and efficacy of rosemary extract and/or its bioactive ingredients when they are administered topically for acne therapy”, no adverse effects were observed in the experiments.
There was no cytotoxicity to any of the cells, no apparent irritation, such as ear swelling and redness, and no increase in levels of neutrophils, another type of inflammatory chemical. They mentioned in the conclusion that “our results indicated that a sole injection of rosemary extract did not cause either skin irritation or inflammation”.
The many compounds of rosemary extract
That’s not the only excellent study directly examining rosemary extract’s effect on acne bacteria. This older one from 2007 gave detailed results on how the extract virtually annihilated p.acnes bacteria itself. Scientists led by Dr G observed significant changes in the morphology and size of p.acnes bacteria.
Firstly, with increasing concentration of the rosemary essential oil, the bacterial bodies were severely damaged. The length, height, and width of p.acnes were all reduced. When the dosage was increased, the length, width and height of the p.acnes were reduced by 42.56%, 92.00% and 41.58%, respectively. A crushing reduction, in other words.
Apparently, when rosemary extract was applied, 1) treated bacteria lost their native shape, 2) the cell wall morphed and lost its shape, 3) the cells of the cell wall began to shed uncontrollably, 4) cytoplasm leaked out the bacterial body, and 5) the bacteria finally died. The p.acnes was pretty much obliterated.
We have two studies showing that rosemary extract eliminates a main formation point in acne. So far, rosemary extract can 1) lower inflammation from p.acnes, and 2) kill p.acnes itself.
There’s rosmarinic acid, carnosol, and carnosic acid. By weight, the main constituents of rosemary oil, a key component of rosemary extract, are bornyl acetate (20.27%), caryophllene (13.61%), eucalyptol (12.84%) camphor (6.41%), camphene (4.19%), borneol (3.61%), and α-caryophyllene (2.53%). Rosemary extract also contains ursolic acid and luteolin. Some of the best compounds are…
Cineol (eucalyptol) – eucalyptol is a common plant compound most notably found in eucalyptus oil. By weight, it’s the most abundant compound, forming 35-45% of rosemary oil. Eucalyptol has a pleasant spicy taste and aroma and hence is actually one of the 599 additives added to cigarettes.
Interestingly, eucalyptol is toxic to many varieties of bacteria; it’s one of the main active ingredients in antibacterial mouthwashes such as Listerine. It also has strong enough anti-inflammatory properties that it’s an ingredient in many cough drops. Elsewhere it’s used in many flavourings, fragrances and cosmetics. Eucalyptus oil is also a natural insect repellent for pests like mosquitoes.
Does it cure acne – eucalyptol doesn’t have any studies showing that it reduces acne inflammation directly. However, this study found that eucalyptol reduced lung inflammation in mice exposed to cigarettes smoke. This double-blind placebo controlled trial found that eucalyptol could reduce lung inflammation in asthma patients.
This study found that eucalyptol reduced inflammation of brain amyloid plaques in Alzheimer’s patients. The best study I’ve found concluded that eucalyptus oil could reduce sebum production, by reducing the size of the sebaceous glands, and could thus control acne.
Rosmarinic acid – the signature compound of rosemary extract. First discovered in 1958, this is structurally similar to the healthy caffeic acid found in coffee beans. Low levels of rosmarinic acid are found in many herbs, but rosemary oil and perilla oil are the famous sources. Perilla oil is used in traditional Japanese medicine to combat allergies.
According to studies on rats, rosmarinic acid is absorbed directly into the skin. The big question is: what does it do when it gets there?
Does it cure acne – there’s a goldmine of great studies on rosmarinic acid. This 2004 study tested the effect of a perilla oil extract containing 68% rosmarinic acid on skin inflammation. Rosmarinic acid had a strong power to reduce neutrophil production. Neutrophils are inflammatory chemicals which spew out free radicals to break down dying cells. They’re healthy in moderation, but in excess they can bombard even your healthy skin cells. Rosmarinic was shown to reduce free radicals as well, in particular lipid peroxides, and thiobarbituric reactive substances, a by-product of lipid peroxide activity. Lipid peroxides are the most potent free radical at causing acne.
This study found that oral rosmarinic acid lowered lipid peroxides in the brain of rats, which should translate when applied topically. This 2009 study is truly superb. It again examined rosmarinic acid and inflammation and like rosemary extract itself, observed reductions in interleukin-6, interlukin-1beta, TNF-alpha when applied topically. However, the study then took things to the next level, as rosmarinic acid also increased skin levels of glutathione, the all-important acne antioxidant, while simultaneously inhibiting both lipid peroxide and reactive oxygen species production.
Rosemary extract has stronger antioxidant power than even ascorbic acid (vitamin C), according to this study. Rosemary extract applied to cells successfully scavenged both peroxide and superoxide free radicals.
Interestingly, this study fed rats rosmarinic acid alongside lycopene, the well-known medicinal compound from tomatoes and watermelon, and found that while both reduced the oxidation of LDL cholesterol very well, they had a synergistic effect when combined. In other words, these studies alone may not reveal rosemary extract’s true strength; rosmarinic extract could be even better for acne in a natural package with carnosol, cineol, carnosic acid, and so on.
Alpha-pinene – a diterpene antioxidant found in rosemary extract, and also juniper berries, eucalyptus oil, and tea tree oil.
Does it clear acne – almost certainly yes; two studies have been conducted directly on p.acnes bacteria.
In the first study, scientists set out to extract natural compounds from eucalyptus and guava leaves with the goal of discovering a new natural acne cure. They extracted the oils and tested both against p.acnes bacteria. Both guava oil and eucalyptus oil showed good antimicrobial activity against p.acnes, and the good news regarding rosemary extract is that the main constituent of the guava oil was alpha-pinene.
The second study analysed the alpha-pinene found in tea tree oil. The compounds terpineol-4-ol, alpha-terpineol, and alpha-pinene were all found to be active against staphylococcus aureus, Staph. Epidermidis and Propionibacterium acnes. These big benefits are not surprising, as according to that study, alpha-pinene is considered to be a natural “broad spectrum antibiotic”.
Carnosol – a phenolic diterpene antioxidant found in rosemary and mountain desert sage. First discovered in 1964. Rosemary extract contains two compounds, called carnosol and carnosic acid, however carnosol is a derivative of carnosic acid and the subject of most studies. Carnosol has been studied for anticancer effects on a wide variety of cells. Carnosol and carnosic acid make up 5% of rosemary leaves, and is believed to account for 90% of antioxidant activity. That’s very interesting, seeing as rosmarinic acid is already a potent antioxidant.
Does it clear acne – this study found that purified carnosol and carnosic acid are powerful inhibitors of lipid peroxidation. Carnosol and carnosic acid reportedly inhibit inflammation at the genetic level (study), and a big review of studies from 2011 called carnosol “a promising anti-inflammatory agent”. Carnosol has been shown to inhibit many different pro-inflammatory messengers, including COX-2 (study) and NF-kappaB (study).
The best study I’ve seen examined the effect of carnosol on inflamed mouse skin and observed greatly reduced COX-2, IL-1B and TNF-a activity. Carnosol soothed the swollen mouse ear substantially. The scientists concluded that carnosol can regulate genes related to inflammation, rather than simply lowering levels of the chemicals.
Unique power alert – UVB radiation resistance
However, there’s one acne benefit which isn’t so common in natural acne treatments: the power to increase your skin cells’ resistance to UV radiation.
First we have a new 2016 study published just last month which tested rosmarinic acid on cells. Thanks to its antioxidant powers, rosmarinic acid reversed nearly all the oxidative damage caused by ultraviolet light from sunlight. It could reverse a depletion in superoxide dismutase (an antioxidant) and destroy free radicals produced by sunlight’s reaction with skin.
The big question is whether rosemary extract itself retains the power or whether one of the other compounds negates it by increasing UV sensitivity. Luckily, this study found that it does.
Scientists tested both citrus and rosemary extract on UV-induced damage to skin cells and on human volunteers. A combination of the two led to higher survival rates in the cells exposed to UV radiation. In the oral human group, taking a combination of citrus and rosemary extract for eight weeks increased their skin’s minimal erythritol dose (MED) by 34%.
The MED is the lowest amount of sunlight that can cause damage to the skin, so the higher your MED is, the more sunlight you can cope with. Taking the combination of citrus and rosemary extract for 12 weeks resulted in a 56% increase in the MED.
Neither of those experiments applied rosemary extract directly to human skin. However, these treatments generally function by either increasing antioxidant levels or through their own antioxidants which build into skin cells. Hence, applying rosemary extract directly to the skin should increase the minimal erythritol dose even further.
If rosemary extract does give your skin a UVB-proof armour, then you can enjoy more sunlight without harm, which will allow you to 1) not be so restrictive in your lifestyle, and 2) make more vitamin D from sunlight.
Right now, rosemary extract ranks similarly to thyme oil: I won’t give it an official endorsement, simply because we lack first hand stories. Unlike tea tree oil or grapeseed oil, we don’t have a vast catalogue of testimonials on acne forums or studies on its side effects.
The first study did comment that rosemary extract caused no irritation, burns, or additional inflammation, but with such a wide array of natural compounds, it’s possible that sensitivity among acne patients may be more common than grapeseed oil, tea tree oil, rose water, honey, or other great topical treatments.
Any downside is possible because we lack real world data. For instance, what if rosemary extract has a tendency to dry out the skin?
The reality is shrouded in mystery right now. It’s highly likely that more acne patients will jump aboard the rosemary extract train as they stumble across the excellent study above. Only then will we discover the truth.
Nevertheless, the studies above are highly promising. Rosemary extract is loaded with anti-inflammatory compounds and has enough antioxidant strength to build an armour against UVB radiation directly into your skin. It’s an excellent choice for experimentation.
Every single essential oil analysed on this website so far has had just as many great studies to its name as traditional treatments like benzoyl peroxide.
Yet again, it shows us how there’s a whole world of natural treatments out there which might revolutionise your skin, as opposed to three or four default traditional ingredients.
Thanks for reading!