Kaffir Lime Leaves (Makrut Lime): Flavor, Chemistry, Uses and the Name

Bend a fresh kaffir lime leaf and you get one of the sharpest citrus smells in the kitchen. In one 2023 study, a single compound, citronellal, made up 77.7% of the leaf oil.¹ The leaves come from Citrus hystrix, a small citrus tree of tropical Asia, and they season curries, curry pastes and soups across Southeast Asia. In Thailand the tree is called makrut, and many cooks, shops and food writers now use that name because “kaffir” is a racial slur in South Africa.²

At a glance

The plant

Kew’s Plants of the World Online describes Citrus hystrix as a shrub or tree of the wet tropics, native from the eastern Himalaya to southern China and Wallis Island.³ The Plant Resources of South-East Asia handbook (PROSEA) is more cautious. It says the species’ origin isn’t known, but that it’s widely naturalized in Malesia, Sri Lanka and Burma and often grown in home gardens.⁴ Kew lists 47 synonyms for the species, among them Citrus macroptera and Citrus papeda.

PROSEA gives the leaves as broadly ovate to ovate-oblong, 3 to 15 cm long, and the fruit as a green to yellow berry 5 to 7 cm across with very bumpy skin. It says the juice is used for seasoning and drinks, but the fruit’s main use seems to be as an insecticide, for washing the head and for treating the feet against land leeches.⁴

Flavor and the compounds behind it

The leaves smell intensely of lime peel with a floral, almost lemongrass-like edge, and a little goes a long way.

The chemistry points to citronellal. A 2023 study steam-distilled leaf oils from four citrus species, with C. hystrix leaves collected from orchards in Negeri Sembilan, Malaysia. Citronellal was the main constituent of the makrut leaf oil, at 77.7%. That oil also had the highest share of oxygenated monoterpenes of the four, and it contained sabinene (3.0%) and citronellol acetate (2.8%), which the authors found only in this species. Limonene made up just 0.2% of the makrut leaf oil.¹

That’s one set of samples from one orchard’s leaves. It shows what can dominate the leaf’s aroma, not a fixed spec. You’ll often read that limonene is responsible for the leaves’ fragrance, and this analysis doesn’t back that up.

How the leaves are used

The leaves season food. Named sources get more specific:

• Thai curry pastes and soups. Britannica lists makrut lime leaf with lemongrass, garlic and other herbs in the region’s thick curry pastes.⁵ SBS Food reports that Sydney restaurateur Vinita Chumsri puts julienned leaves into Panang, green and hor mok curry pastes and uses bruised leaves in coconut and tom yum soups.²
• Infusing. The same article says the leaf is often used to infuse curries. Whole leaves usually stay in the pot and get pushed aside when you eat, like bay leaves.
• Raw, finely sliced. Restaurateur Palisa Anderson tells SBS Food she slices the leaves finely through a warm salad and always adds them at the end, never during heating.²

The midrib is tough, so strip it out before slicing.

Buying and storage

Fresh leaves should be glossy, dark green and stiff, with a strong smell when you bend them. You can also freeze fresh leaves in a sealed bag instead of buying dried. We found no published study or shelf-life figure for makrut leaves from a regulator, standards body or extension service.

Health claims

The National Center for Complementary and Integrative Health has no fact sheet on makrut lime.⁶ The 2023 study above measured antioxidant activity in lab assays and tested the leaf oil against a human cervical cancer cell line in culture.¹ Those are lab results on a concentrated oil. They don’t show that eating the leaves prevents or treats any disease, and we’re not claiming that. Claims that the leaves protect teeth, ease acid reflux or treat arthritis when rubbed on the skin have no support from any systematic review or health agency we could find.

Where the name comes from

“Kaffir” comes from the Arabic kafir, “unbeliever, infidel,” according to the Online Etymology Dictionary. It dates the word’s use for Bantu peoples in South Africa to 1731 and says it’s been a term of abuse since at least 1934.⁷ SBS Food writes that in South Africa it’s a racist slur comparable to the “n” word.²

How the word got attached to a lime is less clear. SBS Food reports that the Scottish botanist H.F. Macmillan assigned the name in his 1910 Handbook of Tropical Gardening and Planting, and that the word there referred to an ethnic group in Sri Lanka.² We haven’t seen Macmillan’s book, so that account is SBS Food’s. Other origin stories circulate, including one tracing the name to a nineteenth-century British reference text. We found no source for those.

The Thai name is makrut. We keep “kaffir lime leaves” in this page’s address because it’s still what many readers search for, and we use makrut alongside it.

Substitutes and comparisons

Nothing else reproduces that citronellal-heavy aroma. Lime zest with a little lemongrass gets you part of the way. See kaffir lime leaves substitutes for options, and these related pages:

• Lemongrass, its usual partner in Thai curry paste
• Lemongrass substitutes
• Thai spices
• Curry paste vs. curry powder