Boswellia is a gum resin from Boswellia serrata, the Indian frankincense tree, which grows in the dry hills of India. When the bark is cut, it weeps a fragrant resin that hardens into pale tears. Related species give us the frankincense used in incense and perfume.
In Ayurveda, where it is known as salai guggul, boswellia resin has traditionally been used to support joint comfort. Its main compounds of interest are boswellic acids, including one called AKBA (acetyl-11-keto-beta-boswellic acid). Researchers have studied boswellia extracts in small trials looking at joint comfort and mobility, and while some results are encouraging, the evidence is still limited and it has no authorised health claim.
On labels you will see boswellia, Boswellia serrata gum resin extract, Indian frankincense or a branded extract name. Many extracts are standardised to a percentage of boswellic acids or AKBA, which is the most useful figure for comparing products, since raw resin and concentrated extracts differ a lot.