Some people with acne use topical (applied to the skin) apple cider vinegar as a natural remedy in an attempt to control their acne. While anecdotal reports are mixed, and while there are no studies concerning topical vinegar’s effects on acne, there is scientific evidence indicating that vinegar has antibacterial properties and contains antioxidants, both of which might be helpful in treating acne. However, there is no evidence that vinegar helps with other aspects of acne such as inflammation or wound healing.
First, let’s look at what vinegar is, and then we will consider why it might be useful for treating acne.
What Is Vinegar?
Vinegar is a natural food product that is made through a process called fermentation. Fermentation uses yeast and bacteria to convert sugar into alcohol or acids. Vinegar fermentation is a two-step process:
- In the first step, yeast converts sugar from a carbohydrate-containing food such as apples, grapes, or grains into alcohol.
- In the second step, a type of bacteria called Acetobacter turns the alcohol into acetic acid, which is the main component of vinegar.1-4
Fermentation of different foods results in different kinds of vinegar. For example, fermenting apple cider results in apple cider vinegar, fermenting wine results in wine vinegar, and fermenting berries results in berry vinegar.1,3,4
Interestingly, while most vinegar is produced commercially, anyone can make vinegar at home. According to a 1976 chapter in the book series Advances in Applied Microbiology, “Nearly any unfortified wine or beer when exposed to the atmosphere will develop an acidity which, in many cases, results from the action of Acetobacter in converting the ethanol to acetic acid. Under normal household conditions, the conversion occurs quite slowly and there are no sharp lines of demarcation between the categories of wine, old wine, sour wine, and vinegar.”2
Vinegar is mostly water and acetic acid, but it also contains a variety of other compounds in small amounts, including vitamins, mineral salts, amino acids (molecules that form the basis of proteins), various acids such as lactic, citric, and malic acids, and a group of compounds called flavonoids. These additional compounds give vinegar its characteristic flavor. Both acetic acid and flavonoids could also contribute to therapeutic effects on acne; we will discuss these effects later in this article.2,5
How Has Topical Vinegar Been Used in Medicine?
People have used apple cider vinegar medicinally for more than 5,000 years for a variety of ailments, including the following:
- In 400 B.C., Hippocrates, a Greek doctor who is considered to be the father of modern medicine, prescribed a mixture of honey and apple cider vinegar to cure diseases.2,3
- During the American Civil War in the 1860s, doctors used apple cider vinegar to disinfect soldiers’ wounds.3
- According to a 1976 chapter in the book series Advances in Applied Microbiology, apple cider vinegar has also been used in “[lotions] to treat lameness, poison ivy, shingles, night sweats, burns, varicose veins, impetigo, and ringworm.”2
How Might Topical Apple Cider Vinegar Help Treat Acne?
While acne is primarily an inflammatory condition, it has a significant bacterial component, as a type of bacteria called P. acnes has been implicated in acne development. Therefore, any substance that is effective against these bacteria might be beneficial in treating acne.
Vinegar has antibacterial effects, and in fact, people have been using it as an antibacterial agent for thousands of years, long before the discovery of antibiotics as we know them. According to a book series Advances in Applied Microbiology, “Possibly vinegar was the first antibiotic known to man, a bacterial product antagonistic to other microorganisms.”2
Past research has indicated that acetic acid, the main ingredient in vinegar, has broad spectrum antibacterial activity against a class of bacteria called gram-negative bacteria. P. acnes is not a gram-negative bacteria however. It is a gram-positive type of bacteria. Whether this reduces the chance that vinegar could kill it remains uncertain.6
The following studies confirm that vinegar can in fact fight bacteria very well:
A 2009 study in the journal Burns confirmed this. The authors of this study concluded, “The tests showed excellent bactericidal effect of acetic acid, particularly with problematic [g]ram-negative bacteria.”7
Similarly, a 2013 study in the The Journal of Hospital Infection demonstrated that acetic acid at concentrations between 0.166% and 0.625% was effective against several antibiotic-resistant types of bacteria. The authors also found that, as an antiseptic (substance to prevent or treat infection), acetic acid performed at least as well as currently used antiseptic products.6
While scientists believe that the antibacterial action of topically applied vinegar is related to its acidity (low pH), many researchers think that some of the compounds present in vinegar may contribute to this effect as well.
As a 2009 chapter in the book Complementary and Alternative Therapies in the Aging Population states, “The [antibacterial] properties of vinegar are well documented and relate directly to the pH-lowering effect of acetic acid; yet it is possible that some inhibitory compounds other than acetic acid may be present in vinegar.”8
As we can see, vinegar’s antibacterial properties are well known and are effective against a wide variety of bacteria. Whether these effects apply specifically to acne is undetermined, as no studies have looked at this, but vinegar may very well be effective against the bacteria present in acne.
Vinegar also contains several compounds, including flavonoids, that are antioxidants. Antioxidants are molecules that prevent cell damage from harmful molecules called free radicals. This is important to acne because the damage from free radicals on the skin can result in inflammation and skin breakouts. Antioxidants might help treat acne by preventing free radicals from harming the skin. Antioxidants also protect the skin by preventing external toxins from penetrating beyond the outermost layer of skin. A low amount of antioxidants near the skin hair follicles and skin oil glands has been implicated in acne development.
According to a 2014 article in the Journal of Food Science, “Bioactive substances such as polyphenols [for example, flavonoids] and vitamins in different types of vinegar defend against oxidative stress due to their significant antioxidant activity.”10
What Topical Vinegar Does Not Treat
While vinegar has well-documented antibacterial and antioxidant properties, both of which might be at least somewhat effective for acne, there are several other aspects of acne that topical vinegar cannot treat and may actually aggravate.
Wound Healing. Medically speaking, acne lesions are wounds. Proper wound healing is important in acne treatment, not only for clearing up the lesions themselves, but also for preventing scarring. Acetic acid does not have wound healing properties, and in fact, in concentrations of more than 10%, acetic acid can irritate wounds and cause inflammation.10,11Most vinegar on store shelves contains 4-9% acetic acid.12
Inflammation. Acne is primarily an inflammatory condition. There is no scientific evidence that vinegar has anti-inflammatory effects. In fact, acetic acid at concentrations of more than 10% can cause inflammation.10
Cell Overgrowth. Acne is caused in part by overgrowth of skin cells within pores. There is no evidence that vinegar can reduce this overgrowth in any way.
Side Effects of Topical Vinegar
Vinegar has been used topically for thousands of years, and people may assume that it is safe. This is generally true, and no side effects have been reported in people using common topical vinegar. However, as mentioned above, more concentrated acetic acid can cause wounds and inflammation.
A 2015 article in the journal Advances in Wound Care explains, “Acetic acid is considered harmless below concentrations of 5%, as in vinegar, but in concentrations between 10% and 30% acetic acid is corrosive.”10
Warning: It is important to note that acetic acid can be concentrated to form products with 100% acetic acid. This type of acetic acid is called glacial acetic acid, and it is harmful to skin. Even when diluted, glacial acetic acid can cause burns when applied to the skin, and may eventually cause scarring. Glacial acetic acid also causes skin damage that can result in absorbing the acid through the skin and into the body. If this happens, damage to organs like the kidneys and liver can occur.13
How to Do It:
If you would like to try adding apple cider vinegar (ACV) as a toner to your skin care regimen, follow these simple steps:
- Start with an organic, unfiltered apple cider vinegar.
- Always dilute the ACV with filtered/distilled water. In a small glass container, mix ACV with filtered water. Start with 1 tablespoon of ACV and mix with 2-3 tablespoons of water. (If you have sensitive skin, dilute the ACV further by using more water. You can try building up to using less-diluted ACV over time.)
- Cleanse your skin using your bare hands and a mild facial cleanser, and gently pat dry with a towel. Remember, physical irritation of the skin makes acne worse, so stay ultra-gentle.
- Soak a cotton ball or cotton pad with the ACV mixture and very gently apply to the skin. Don’t scrub. Stay exceedingly gentle.
- Wait until the ACV mixture has dried. You can now apply other products if you wish.