Indigenous to Africa, Vitellaria paradoxa, better known as the shea or shi tree, is a member of the Sapotaceae family. It has long been used in traditional medicine in sub-Saharan West Africa (as far west as Mali) as well as parts of East Africa (as far east as Uganda and Ethiopia) for its anti-inflammatory and analgesic properties.1,2
Some indications in traditional Nigerian medicine include nasal congestion, scabies, and ulcers.2 In addition, anecdotal success in treating keloids has been reported in association with traditional African remedies, including shea butter and boa constrictor oil.3 Antioxidant activities have also been linked to V. paradoxa.4 Given such purported properties, it is not surprising that demand for shea kernels and butter has steadily increased in recent years for various purposes, including use as food (particularly as a cocoa butter additive in chocolate) and in medical and cosmetic products.2,4 The use of shea butter in skin care is attributed to its hydrating qualities and reputed effectiveness in softening scars.3
Shea butter contains fatty acids that have been shown to improve the skin barrier. These include palmitic, stearic, and linoleic acid. It also contains the fatty acids oleic and arachidic. Shea butter also has phenolic components that function as antioxidants.
In 2010, Akihisa et al. evaluated the inhibitory effects of four triterpene acetates and four triterpene cinnamates isolated from the kernel fat of V. paradoxa against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation in mice. All of the tested compounds showed considerable anti-inflammatory activity (ID50 values ranged from 0.15 to 0.75 micromol/ear). Lupeol cinnamate displayed the greatest anti-inflammatory activity, on carrageenan-induced edema on rat hind paws. All eight substances also exhibited moderate inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) in Raji cells as a primary screening test for tumor promoter inhibitors. Using 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter in a two-stage carcinogenesis model in mice, the investigators also found that lupeol cinnamate inhibited skin tumor promotion. They concluded that the triterpenes and triterpene esters found in shea nuts and shea butter are significant anti-inflammatory and antitumor-promoting agents.2
The next year, Akihisa et al. determined the triacylglycerol and triterpene ester fraction composition of the kernel fats of the shea tree from 36 samples from Cote d’Ivoire, Ghana, Nigeria, Cameroon, Chad, Sudan, and Uganda. There were no significant differences in the composition of the triterpene ester fractions between West African and East African plants. Generally, though, West African shea kernel fats contained higher levels of high-melting triacylglycerols (e.g., stearic-oleic-stearic) and triterpene esters.6
Also that year, Olaitan et al. found that shea butter (as well as boa constrictor oil) was effective in suppressing the in vitro growth of normal and keloid fibroblasts.3
In 2012, Verma et al. used the lipopolysaccharide (LPS)-induced murine macrophage cell line J774 to investigate the anti-inflammatory properties of the methanolic extract of shea butter. They found that shea butter extract dose-dependently reduced, to a significant degree, the levels of nitric oxide, tumor necrosis factor (TNF)–alpha, as well as interleukin (IL)-1beta and IL-12 in the culture supernatants. In addition, the botanical extract suppressed IkappaB phosphorylation and NF-kappaB nuclear translocation as well as the expression of pro-inflammatory enzymes, inducible nitric oxide synthase (iNOS), and cyclooxygenase (COX)-2. The investigators attributed the anti-inflammatory activity of the extract to its inhibitory impact on LPS-induced iNOS, COX-2, TNF-alpha, IL-1beta, and IL-12 mRNA expression.1
In 2014, Honfo et al. conducted a literature review indicating that shea pulp is laden with vitamin C and the kernels contain copious fat (butter), which is used in food, drugs, and cosmetics.4
Notably, shea butter is also an ingredient in the topical nonsteroidal anti-inflammatory drug (NSAID) atopiclair, which has shown efficacy in alleviating pruritus in adults with mild to-moderate atopic dermatitis.7
Shea butter has long been incorporated into traditional medical practice in West and East Africa based on observed anti-inflammatory and analgesic characteristics. Such uses are compelling and often the basis for systematic scientific investigation. That said, there remains a dearth of experimental and clinical research on the potential cutaneous benefits of topically applied shea butter. Current data and traditional applications provide ample reason for continued research into this popular botanical agent.