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The tamanu tree grows along the central coast of Vietnam. Its seeds yield a deep green oil used for acne and sensitive skin. This piece records the tree, the seed, and how Lê Mai uses it.

The tamanu tree along Central Vietnam's coast

Tamanu, scientifically Calophyllum inophyllum, is a tropical coastal tree native to Vietnam. It grows from Quảng Bình southward to Bến Tre. The tree is 8 to 12 metres tall, with a broad canopy, tolerant of salt and sea wind.

The flowers are small, white, in clusters. The fruit is round, 2 to 3 centimetres across, green when young and brown when ripe. Inside is a hard seed containing the oil-rich kernel.

Tamanu is not an industrial crop. Each season, local people gather fallen fruit beneath wild trees. A mature tree yields about 100 kilograms of fruit per year.

The nut and how it is pressed

Tamanu fruit is sun-dried for several days until the shell splits naturally. The kernel inside is pale cream when first exposed, darkening to deep brown after another four to six weeks of curing.

This curing matters. Oil from fresh kernels has no distinctive scent and a pale colour. After enough curing, the phenols in the seed oxidise, producing the deep green colour and characteristic scent of mature tamanu oil.

Cold-pressing below 60°C preserves the active compounds. One kilogram of dried kernel yields about 200 to 250 grams of oil. Freshly pressed oil is deep green, nearly black, thick and sticky.

Calophyllolide and calanolide A

The two main actives in tamanu oil are calophyllolide and calanolide A. Both belong to the 4-phenylcoumarin class, found only in tamanu and a few close relatives.

Calophyllolide is anti-inflammatory. In vitro studies show it inhibits COX-2 and reduces local prostaglandin production. The mechanism resembles some synthetic anti-inflammatories but is weaker and safer for topical use.

Calanolide A is antibacterial, particularly against some gram-positive bacteria implicated in acne. It has also been studied for antiviral activity, though that application remains in early research.

For acne and scarring

On inflamed acne, tamanu oil is applied directly to lesions or diluted 10 to 30 percent in another carrier oil. A few drops at night, left overnight.

The anti-inflammatory action reduces redness within 12 to 24 hours. The antibacterial action reduces local bacteria, preventing spread. Effects are most visible on small inflamed papules, less so on deep cysts.

On older acne scars, tamanu is used consistently for 8 to 12 weeks. Animal studies show it stimulates collagen production and tissue regeneration. Human results are mixed, but most reports describe softer, fading scars.

For sensitive skin and infants

Tamanu is generally well tolerated on sensitive skin, but it must be diluted. Pure undiluted oil can cause mild irritation in some people due to its viscosity and slightly acidic pH.

For children twelve months and older, dilute 5 to 10 percent in jojoba or sweet almond oil. Patch test on the inner forearm for 24 hours before broader use. Not for infants under twelve months.

Pregnant women may use tamanu from the second trimester. There are no specific contraindications, but dilution remains the safest approach.

Tamanu in Bách Lý Hương soap

Lê Mai uses tamanu oil in the Bách Lý Hương soap formula at 8 to 10 percent of total oils. This ratio is enough to retain anti-inflammatory activity after saponification without making the bar too soft.

The deep brown colour of Bách Lý Hương bars comes from oxidised tamanu. The oil's distinctive scent combines with the thymol from dried thyme powder, producing a complex base note.

The skin meets this soap every day, in 30 to 60 second contact. The dose of tamanu is small but consistent, enough to sustain its anti-inflammatory and antibacterial effect on acne-prone skin.

A tree by the coast. A dry fruit. A deep green oil.

Tamanu was there before Lê Mai knew of it. Still there. Still giving oil.