Thai Basil vs. Holy Basil: Anise Horapha and Peppery Kaphrao

Ordered phat kaphrao and tasted anise? That may have been Thai basil standing in for holy basil, and the swap changes the dish. The two aren’t even the same species: Thai basil (horapha) is an anise-scented form of sweet basil, Ocimum basilicum, while holy basil (kaphrao, tulsi) is Ocimum tenuiflorum, a peppery basil sometimes called “hot basil.”¹ A 2018 study of basils eaten in Thailand put the two in different aroma groups, with Thai basil’s oil led by estragole and holy basil’s by methyl eugenol.² And at the store, purple stems prove nothing.

Side by side

What the chemistry shows

The Chiang Mai University study analyzed five basils “used as food ingredients in Thailand,” all grown at the same research center, which makes it a rare like-for-like comparison.² The figures are concentrations in the oil, not percentages.

Source: Tangpao, Chung and Sommano, 2018.²

“Not among the top three” means the paper’s summary doesn’t report it for that basil, not that it’s absent. Two things jump out. The two basils share none of their leading compounds. And the red holy basil’s oil is far more concentrated in its lead compound than the white’s, so two bunches sold as holy basil can be quite different.

Flavor and strength

Holy basil often gets described as fiercely spicy, even numbing. The cooks we checked are more measured. Andy Ricker calls it a basil with a peppery flavor and a distinctive aroma.¹ Pailin Chongchitnant of Hot Thai Kitchen says it smells less floral and more peppery than Thai basil, and is milder too.⁷ The Herb Society of America calls its taste astringent and its aroma strong.⁵ We found no source for the claims that raw holy basil numbs your tongue like Sichuan pepper or gets spicier as it cooks.

In the Thai cooks’ accounts, Thai basil is the louder of the two. Sherri Pengjad of Thai Foodie calls it bolder and more aromatic than Italian basil and says it goes into green curry right before serving for its licorice-like aroma. She also finds it sturdier than Italian basil in hot dishes.⁴

How each is used

• Holy basil: phat kaphrao. The stir-fry is named after the herb. Ricker’s version uses chicken, and he adds the leaves at the very end, stirring just until they wilt and turn very fragrant, about 15 seconds.¹ Chongchitnant’s uses beef,⁷ so the dish isn’t tied to one meat.
• Holy basil: tea and ritual. Holy basil is considered sacred in Hinduism and is used as a culinary herb throughout Southeast Asia.
• Thai basil: curries and stir-fries. Pengjad stirs it into green curry at the end.⁴ Drunken noodles and red curry usually take it too.
• Thai basil: raw, at the table. Andrea Nguyen lists Thai basil (húng quế) on her pho garnish plate, adding it when it’s at its peak in warmer months, and tells readers to add or subtract herbs as they like.⁸

Both are delicate herbs. Long heat can cost them flavor and aroma, so both go in at the end of cooking.

Telling them apart when buying

Mislabeling tends to run one way. Ricker warns that “holy basil” labels sometimes end up on purple-stemmed Thai or sweet basil, and notes that Indian grocers may sell true holy basil as tulsi.¹ So purple stems don’t prove anything. PROSEA describes sweet basil’s stems as ranging from light green to dark purple.⁹ Smell is the better test: anise means Thai basil, pepper means holy basil (which lines up with the aroma groups above).

Can one stand in for the other?

Yes, by volume, but you’ll get a different result. The published figure treats them as interchangeable in amount, not in flavor.

What the cooks say about the result:

• Thai basil for holy basil. Chongchitnant says you can use Thai basil and the dish will be just as tasty, but it tastes quite different; she prefers Italian basil as the closer match. She also suggests that restaurants serving “holy basil” stir-fries may be using Thai basil because holy basil isn’t available.⁷ SheSimmers says that if you only have sweet basil you can use it, but should call the dish Pad Bai Horapha.¹⁰
• Holy basil for Thai basil. Pengjad says holy basil will work in a pinch, but the dish will taste less traditional.⁴

For other options see Thai basil substitutes and holy basil substitutes.

Safety

Each basil’s leading compound is one regulators have looked at. Germany’s BfR notes that safrole, methyl eugenol and estragole showed mutagenic and carcinogenic properties in animal studies, and concluded in 2022 that the risk from foods containing them can’t yet be conclusively assessed.¹¹ The EU Scientific Committee on Food couldn’t set a safe exposure limit for estragole in 2001.¹² Neither body singles out Thai or holy basil or tells people to stop eating basil. Holy basil isn’t on the FDA’s GRAS spice list, which names sweet basil,⁶ but we draw no safety conclusion from that. Health claims for tulsi supplements are covered on our holy basil profile.

What isn’t known

• The Thai study grew one sample of each basil at one site. No source says how much the oils vary between farms and markets.
• No source we found measures how often “holy basil” on sale is really Thai or sweet basil.
• We couldn’t trace claims that holy basil numbs the tongue, gets spicier with cooking, or is often called “Thai holy basil,” or that Thai basil goes into Taiwanese three-cup chicken.

Related

• Profiles: Thai basil, holy basil and basil
• Substitutes: Thai basil substitutes and holy basil substitutes
• Comparisons: basil vs. Thai basil, holy basil vs. basil, Genovese basil vs. Thai basil and cinnamon basil vs. Thai basil
• More: lemon basil, how to store basil and too much basil