BHT stands for butylated hydroxytoluene, an organic compound that is used in cosmetics and personal care products for its antioxidant properties.
BHT is a lipophilic (fat soluble) organic compound that is chemically a derivative of phenol. Phytoplankton, green algae, and three different types of cyanobacteria are capable of producing BHT. This ingredient can also be synthetically produced. BHT is a white, crystalline, odorless solid.
BHT is primarily used as an antioxidant in foods that contains fats and oils, or in packaging material for fat containing foods. BHT is also used in cosmetics and pharmaceuticals. According to WebMD, BHT is used to treat genital herpes and acquired immunodeficiency syndrome (AIDS). Additionally, some people apply BHT directly to the skin for cold sores. BHT works for these conditions by damaging the protective outer layer of viral cells. This may keep the viruses from multiplying and/or doing more damage.
You’ll find BHT primarily in makeup products such as eyeliner, lipstick, blush and foundation, but you can also find it in various other cosmetic products like moisturizers, cleansers, and perfume.
As an antioxidant, BHT helps fight against the deterioration of cosmetic products caused by free radicals known as reactive oxygen species (ROS). Oxygen molecules are normally stable and unreactive because they have an even number of electrons. However, when reactions occur that leave the oxygen molecule with an odd number of electrons, the molecule becomes unstable and highly reactive. Since they are highly reactive, they want to either donate that single electron to another molecule or accept an electron from another molecule so that they can become stabilized. This can lead to the degradation of cosmetic products, so ingredients such as BHT are used to maintain product integrity.
In order to combat ROS, BHT functions as a synthetic analog of vitamin E, primarily acting as a terminating agent that suppresses autoxidation. Autoxidation is a process whereby unsaturated organic compounds are attacked by atmospheric oxygen. BHT stops this autocatalytic reaction by donating a hydrogen atom, which converts peroxy radicals to hydroperoxides. BHT is also known to work synergistically with other antioxidants.
The FDA considers BHT as Generally Recognized As Safe (GRAS) to use as a food additive up to concentrations of 0.02%.
According to EWG, BHT is rated as a 4 on a scale of 1 to 10, with 1 being the lowest health risk and 10 being the highest. The concerns for this ingredient are skin, eye, and lung irritation.
The safety of BHT has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel evaluated the scientific data and concluded that BHT was safe for use in cosmetics and personal care products.
The CIR Expert Panel noted that only limited tests evaluated the effects of BHT on skin. However, studies in which topical application of BHT was used to mitigate the effect of ultraviolet radiation were considered. These studies clearly demonstrated the absence of a photosensitization effect and no sensitization or significant irritation was reported.
Oral exposure to relatively large doses of BHT has resulted in liver and kidney effects. However, the CIR Expert Panel was not concerned with these effects because of the limited dermal absorption of BHT and the low concentrations of use (0.01 to 0.1%) of this compound in cosmetics and personal care products.
BHT is a controversial ingredient because studies have found this ingredient to be both carcinogenic and anti-carcinogenic. One study found that BHT was cytotoxic because it triggered the release of cytochrome c. While cytochrome c isn’t always bad, in this case it caused overactive apoptosis (cell death). After repeated injection in mice, two studies found that BHT caused lung tumors and damage to the mice.
There are a few studies that look at the anti-carcinogenic properties of BHT. One study showed that BHT can prevent photocarcinogenesis because of its antioxidant properties. Other studies have found that BHT can mitigate the effects of other cancer-inducers when pre-fed to rats.
Ultimately, the safety of BHT comes down to whether it is applied to the skin or ingested, as well as the concentration used.
References: Wikipedia, “Butylated hydroxytoluene”, Molecular Pharmacology, 2000 Aug;58(2):431-7, Carcinogenesis, Volume 10, Issue 4, 1 April 1989, Pages 773–775, Cancer Treat Rep. 1986 Apr;70(4):503-7.