Caffeine is being increasingly used in cosmetics and skin care products due to its high biological activity and ability to penetrate the skin barrier, providing benefits such as reducing signs of aging, improving circulation, and protecting skin from the damaging effects of UV light.
Caffeine was discovered in 1819 by German chemist Friedlieb Runge, who isolated the molecule from an Arabian mocha bean. Today, caffeine is the world’s most widely consumed psychoactive drug.
Caffeine is a central nervous system (CNS) stimulant that is well known for its presence in coffee and tea. In addition, caffeine is known to be present in approximately sixty different plant species. The most common sources of caffeine are the beans of the two cultivated coffee plants, Coffea arabica and Coffea canephora, in the leaves of the tea plant, and in kola nuts. When consumed, caffeine reversibly blocks the action of adenosine on its receptor, which prevents the onset of drowsiness induced by adenosine.
In addition to the energy-boosting effects gained from consuming caffeine, there are also benefits of applying caffeine topically. The date that caffeine first emerged in the skin care industry is unknown. However, in 2006, over 140 skincare products containing caffeine were launched in the United States, as compared to just 21 in 2003. The commercially available topical formulations of caffeine normally contain 3% caffeine.
The functions of caffeine in skin care and beauty products are based on the ability of caffeine to scavenge free radicals, improve circulation, protect skin from sun damage, and stimulate hair growth.
Caffeine has some antioxidant properties. The main mechanism involved in the direct reactive oxygen species (ROS) scavenging activity of caffeine is known as radical adduct formation (RAF). This means that caffeine can effectively scavenge the hydroxyl radical (-OH) and the -OCH3 free radical. Caffeine is inefficient for directly scavenging the free radicals -OOH, -OOCH3, and -O2. Free radicals are highly reactive molecules that can attack important cellular components, such as DNA, cell membranes, proteins, etc., which leads to signs of aging. Thus, products that contain caffeine can help to prevent and treat signs of aging.
As a natural stimulant, caffeine causes vasoconstriction (constriction of the blood vessels) when applied to the skin. This function aids in reducing the amount of blood that accumulates under the eyes (a major factor that contributes to dark circles). Additionally, vasoconstriction can firm the skin due to the removal of excess fluids and possible stimulation of the lymphatic drainage system. Thus, eye creams that contain caffeine are thought to help reduce dark circles and puffiness.
Caffeine is often used as an active compound in anti-cellulite products because it prevents excessive accumulation of fat in cells. This alkaloid stimulates the degradation of fats during lipolysis through inhibition of the phosphodiesterase activity. Furthermore, dermatologist Julie Russak, M.D., explains to Women’s Health, “Caffeine dehydrates the fat cells and stimulates circulation, therefore making the skin appear tighter and smoother, says Russak. However, she notes that these effects are temporary and shouldn’t be relied on as long-term solutions.
Clinical studies have found the caffeine can help to protect cells against damage caused by UV radiation and slow down the process of photoaging of the skin. Studies on mice exposed to radiation examined the effects of topical caffeine application. Results from these studies revealed that caffeine has a sunscreen effect on the skin of mice and also inhibited UVB-induced skin carcinogens. Other studies have shown that caffeine helps block the protein ATR (ataxia telangiectasia), therefore protecting skin against UV damage and, ultimately, reducing the risk of skin cancer.
Finally, caffeine has the ability to stimulate hair growth through inhibition of the 5-α-reductase activity. Additionally, caffeine acts as a vehicle to penetrate into the cells and therefore can help to deliver active ingredients into the hair follicle.
The Food and Drug Administration (FDA) includes caffeine on the list of substances Generally Recognized as Safe (GRAS) as a multipurpose food substance. The Cosmetic Ingredient Review (CIR) Expert Panel has deferred evaluation of caffeine because the safety has been established by FDA. However, since caffeine does penetrate the skin it may be sensitizing for some individuals.
References: Skin Pharmacol Physiol. 2013;26(1):8-14, Wikipedia, “Caffeine”, Dermascope, “Caffeine in Skin Care”, Bulletproof Blog, “Eat These Foods for Radiant Skin”, 2017, J. Phys. Chem. B, 2011, 115 (15), pp 4538–4546, Women’s Health, “6 Legit Beauty Benefits of Caffeine”, 2016, Paula’s Choice, “Caffeine”.