Thambaratham (Averrhoa carambola)

Thambaratham, kamrakh in Hindi, is star fruit or carambola, whose five-ridged, waxy fruit cuts into stars. It is a common homestead fruit across South and North-east India. Star fruit contains oxalate and a nerve toxin, caramboxin, which people with kidney disease cannot clear; for them even a few fruits can cause hiccups, confusion, seizures and death. It is a relative of bilimbi.

Botanical name: Averrhoa carambola L.
Family: Oxalidaceae
Tamil: Thambaratham
Hindi: Kamrakh
Sanskrit: Karmaranga
Parts used: Fruit
Habit: Small tropical fruit tree; the star fruit is dangerous for kidney patients
Last updated: 2026-10-27

How to recognise Thambaratham

It is a small, bushy evergreen tree, usually five to ten metres tall.

The leaves are pinnate, with several pairs of soft, oval leaflets that fold at night.

Small, pink to purple flowers grow in clusters on twigs and branches.

The fruit is waxy, yellow-green to golden, with five deep ridges, star-shaped when sliced.

Bilimbi fruit is cylindrical, smoother and much more sour.

Traditional use of Thambaratham

Kitchen

Ripe star fruit is eaten fresh with salt and chilli, and the sour types are pickled or cooked in curries.

Indian food practice

Kitchen

Sliced star fruit is used as a garnish in salads and drinks.

Tropical food practice

Household

Its sour juice is used to clean brass in South and South-east Asia.

Household practice

Modern notes on Thambaratham

Star fruit poisoning in people with kidney disease is well documented, and caramboxin was identified as the toxin in 2013.

Large amounts of juice have also harmed people with healthy kidneys, through oxalate crystals.

The fruit supplies vitamin C and fibre.

Thambaratham safety

People with any kidney disease, or on dialysis, should not eat star fruit at all. Others should avoid drinking concentrated juice, especially on an empty stomach.

Ecology and sourcing

It is native to South-east Asia, probably Indonesia or Malaysia.

Bees pollinate the flowers.

It fruits several times a year in the humid tropics.

Related plants

Also in Oxalidaceae

Questions about Thambaratham

Is star fruit safe?

For most people in small amounts, but never for kidney patients.

What is caramboxin?

A nerve toxin in star fruit.

Is Thambaratham the same as bilimbi?

No. Bilimbi is a sour relative.

Why is Thambaratham called star fruit?

Slices are star-shaped.

Can juice be harmful?

Yes, concentrated juice has damaged kidneys.

Sources

Educational page about a plant. It is not medical advice, not a diagnosis, and not an offer to sell. Traditional use is historical. If you need care, ask a licensed clinician. Questions: hello@meevamed.com.