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What Is the Difference Between Mustard and Karashi? Seed Types, Why Mixing with Water Makes It Hot, and the Ingredients and Allergen Labeling of Dijon, Whole-Grain, and Japanese Karashi

Researched and written by Tadachi (editor)Published

PR This article contains affiliate links to Rakuten Ichiba (“See on Rakuten”). What is written here is based on documents from public agencies and on studies, regardless of whether there are ads. The “See on Amazon.co.jp” and “See on Yahoo! Shopping” links are also affiliate links.

Japanese karashi on oden, yellow mustard on a hot dog, whole-grain mustard served with sausages, Dijon mustard in a dressing. All of them are in the “karashi” family, but they differ quite a lot in heat, in color, and in the ingredient list on the back label.

You also often see questions such as “What is the difference between Japanese karashi and mustard?”, “Why isn’t karashi powder hot until you mix it with water?”, and “Is it true that it isn’t hot if you mix it with boiling water?”

In this article, we check the following against studies, laws, documents from public agencies, and the ingredient lists given by the manufacturers:

  • What kinds of seeds does karashi (mustard) come from (white, brown, black)?
  • Where does the heat come from? Why does it get hot when you mix it with water? What happens if you mix it with boiling water or vinegar?
  • How do Japanese karashi, yellow mustard, Dijon mustard, and whole-grain mustard differ in how they are made and in their ingredients?
  • How do the allergen labeling rules for karashi (mustard) differ in Japan, the EU, Canada, and the US?

Conclusions

  • Mustard seeds come mainly in three kinds: white mustard (Sinapis alba), brown mustard (Brassica juncea), and black mustard (Brassica nigra). Japanese karashi is made from the seeds of the strongly pungent brown type (the oriental type)
  • The seeds themselves and the powder are hardly hot. When water is added, the enzyme “myrosinase” in the seed breaks down the non-pungent compounds (sinigrin and sinalbin) and makes the pungent compounds. In brown and black mustard this is allyl isothiocyanate (volatile, and it hits the nose); in white mustard it is 4-hydroxybenzyl isothiocyanate (not volatile, and the heat is mild)
  • Myrosinase is an enzyme that is weak against heat and acid. The enzyme of white mustard was not active after 10 minutes of heating at 70°C (an experimental result). It has also been reported that the white mustard enzyme almost stops working at pH 4.5. The manufacturer’s instructions are to dissolve it in lukewarm water of about 40°C and leave it for 4 to 5 minutes
  • Under French law, “Dijon mustard” must be made only from black or brown seeds, with the seed coat removed, and “old-fashioned (whole-grain) mustard” is coarsely ground with the coat. The ingredient lists of products in Japan range from just “からし (karashi, mustard)” for powdered karashi to tube products containing salt, starch, vegetable oil, sorbitol, acidulant, flavoring, and more
  • Mustard is subject to mandatory allergen labeling in the EU, the UK, Switzerland, and Canada, but not in Japan (9 mandatory and 19 recommended items) or the US (9 items). It accounted for 6% of the causes of food allergy in a survey of French children, while in Japan’s 2023 national survey it was 1 case out of 6,033 (the survey methods differ, so the numbers cannot be compared directly)

What This Article Features

For people who What we feature Why we chose it (ingredients, etc.) Where
Want to mix from powder and check the heat of Japanese karashi 山清 有機 鬼からし (Yamasei Organic Oni-Karashi) (30 g) The ingredient list (原材料名) is only “有機からし（カナダ産）” (organic karashi, from Canada) Japanese karashi and tube karashi paste
Want to compare with a Dijon mustard without additives ビオスター 有機ディジョンマスタード (Biostar Organic Dijon Mustard) (200 g) The ingredient list has three items: organic mustard, organic brewed vinegar, and salt Dijon mustard
Want to try a whole-grain mustard made without sugar ビオスター 有機粒マスタード (Biostar Organic Whole-Grain Mustard) (200 g) The ingredient list has three items: organic mustard, organic brewed vinegar, and salt Whole-grain mustard
Want to buy at a nearby roadside station (Osaka) 月のアムリタ 粒マスタード (Tsuki no Amrita Whole-Grain Mustard) (in-store only) Mustard seeds, three kinds of vinegar, and salt. No sugar or additives listed Whole-grain mustard

There Are Three Kinds of Mustard Seeds

White, Brown, and Black

Mustard is the seed of a plant in the Brassica family. S&B Foods also explains karashi as “the powdered seeds of karashi-na (mustard greens) of the Brassica family.” The seeds used in cooking are mainly these three kinds (Health Canada assessment, review by Lietzow et al., 2021).

White mustard Brown mustard (mustard greens) Black mustard
Scientific name Sinapis alba Brassica juncea Brassica nigra
Other names Yellow mustard, Western karashi Oriental mustard, the source of Japanese karashi Black mustard
Seed color Pale straw yellow Brown (as the English name says) Blackish reddish brown
Source of the heat Sinalbin Sinigrin Sinigrin
Pungent compound formed 4-hydroxybenzyl isothiocyanate Allyl isothiocyanate Allyl isothiocyanate
Heat Mild Strong Stronger than white or brown, and a little bitter
Main uses American-style yellow mustard, pickles and sausages Japanese karashi, Dijon mustard Dijon mustard (one of the seeds allowed by law)
  • Black mustard pods burst open easily and are hard to harvest by machine, so it came to be used less in the US and Europe. Brown mustard plants are tall and their pods do not burst easily, so they are said to be easier to harvest by machine (Lietzow et al., 2021)
  • Brown mustard is thought to be a species that arose from a natural cross between black mustard and a relative of turnip and napa cabbage (Brassica rapa). This is the relationship called “U’s Triangle,” shown in 1935 by the botanist Woo Jang-choon (born in Korea; his paper was published under the Japanese name “U Nagaharu”), and it has been supported by later genetic studies
  • In Japan, mustard greens are also used as a leafy vegetable. The Food Composition Tables list the alternative names of “karashi-na” as “ha-garashi” and “na-garashi”

Where Is It Grown?

  • In 2019, world production of mustard seed was over 32% in Nepal, 25% in Russia, and 21% in Canada (Lietzow et al., 2021)
  • Health Canada says that Canada accounts for about 35% of world production and about 50% of exports (an assessment from around 2010)
  • Many ingredient lists of products sold in Japan also say “からし（カナダ）” (karashi, Canada), and both S&B Foods’ powdered karashi and its tube Japanese karashi use karashi from Canada

Japanese Karashi and Western Karashi

In Japan, a strongly pungent “wa-garashi (Japanese karashi)” and a mild “yo-garashi (Western karashi)” are sometimes called separately. S&B Foods describes Japanese karashi as having “the strong heat of old Japan,” and Western karashi as having “a mild heat that came from Europe and America.”

It has been used in Japan since long ago. The “Engishiki,” which compiled the ceremonies and systems of the early Heian period, lists “芥子 (karashi)” as one of the crops paid as tax (S&B Foods’ explanation).

Why Mixing with Water Makes It Hot

Diagram of how karashi gets hot. As seeds or powder it is hardly hot; when the seed is crushed, the source of the heat meets the enzyme, and when water is added the enzyme myrosinase works and makes the pungent compound. In Japanese karashi and black mustard (brown and black seeds), sinigrin becomes allyl isothiocyanate, which is volatile and hits the nose. In white mustard (the seed of yellow mustard), sinalbin becomes 4-hydroxybenzyl isothiocyanate, which is not volatile and has a mild heat. The enzyme is affected by heat and acid: after 10 minutes of heating at 70°C, only 0% of the enzyme activity remained for white mustard, 59% for black mustard, and 35% for brown (a test-tube experiment). The enzyme of white mustard is at its maximum of about 50% at pH 5.0 and hardly works at pH 4.5, and in acid conditions the non-pungent compound (nitrile) is more likely to form. The manufacturer (S&B Foods) instructs to dissolve 2 teaspoons of karashi powder in lukewarm water of about 40°C or 1 teaspoon of water, cover with plastic wrap, and leave for 4 to 5 minutes.
Figure: How karashi gets hot, and the effect of heat and acid (click to enlarge)

Inside the Seed, They Are in “Separate Rooms”

Mustard seeds are not very hot even if you bite them as they are or lick the powder. Inside the seed, the compounds that are the source of the heat (a group of compounds called glucosinolates) and the enzyme that breaks them down, “myrosinase,” are kept in separate cells, or in separate places inside a cell.

When the seed is crushed the two meet, and when water is added, myrosinase works and makes the pungent compound. Water is itself an ingredient of this reaction (Lietzow et al., 2021; Barba et al., 2016).

  • Japanese karashi and black mustard: sinigrin → allyl isothiocyanate (allyl mustard oil). It is volatile (turns into gas easily), so it gives a sharp stimulation that hits the nose
  • White mustard: sinalbin → 4-hydroxybenzyl isothiocyanate (benzyl mustard oil). It is not volatile, so the heat of white mustard is milder (S&B Foods’ explanation). This compound breaks down easily in water, and over time it turns into non-pungent compounds (Choubdar et al., 2010, and others)

The reaction goes on even with just humid air. In an experiment that put mustard powder in a humid container, the higher the humidity and temperature, the more allyl isothiocyanate came out, and the faster (Dai et al., 2014).

There is research comparing how heat is perceived with the amount of the compound. In a study of commercial mustards from several brands (from mild to extra hot), the products with more allyl isothiocyanate had a stronger heat that people felt and that lasted longer (Eib et al., 2020).

Allyl isothiocyanate belongs to the same group of compounds as the heat of wasabi and horseradish. In 2004, experiments with animal cells showed that it stimulates a receptor on nerves called “TRPA1” (called ANKTM1 at the time of publication), which is felt as a pain-like stimulation (Jordt et al., 2004). The heat of chili peppers (capsaicin) works by a different mechanism (explained in the chili article).

Bitter Right After Mixing

S&B Foods explains that right after you dissolve karashi powder you may notice bitterness, that this is because the bitter compound sinigrin is still there, and that over time it changes into the pungent compound (allyl mustard oil).

Mixing with Boiling Water or Vinegar Makes It Less Hot

Myrosinase is an enzyme, so it is affected by heat and acid.

Condition What is known Source
Lukewarm water One report says the myrosinase of white mustard seed worked best at 60°C Lietzow et al. (2021) (citing a study by Van Eylen et al.)
Hot water, heating After 10 minutes of heating at 70°C, only 0% of the enzyme activity remained for white mustard, 59% for black mustard, and 35% for brown Okunade et al. (2015) (test-tube experiment)
Vinegar (acid) The myrosinase of white mustard is at its maximum of about 50% at pH 5.0 and hardly works at pH 4.5 BRENDA (enzyme database)
Vinegar (acid) In acid conditions, it becomes easier to form a non-pungent compound called “nitrile” instead of the pungent isothiocyanate Barba et al. (2016)

The manufacturer’s instructions are to dissolve 2 teaspoons of karashi powder in lukewarm water of about 40°C or 1 teaspoon of water, cover it with plastic wrap, and leave it for 4 to 5 minutes. It also dissolves in plain water, but they say that using lukewarm water makes the heat come out more easily (S&B Foods).

(Most of the experiments we looked at here were done in test tubes, with the enzyme extracted or under set conditions. They are not the same as the temperature and time when you mix it in a kitchen.)

Differences Among Japanese Karashi, Yellow, Dijon, and Whole-Grain

Water and salt equivalent of four karashi and mustard products (per 100 g)Values per 100 g of edible portion from MEXT, Standard Tables of Food Composition in Japan (8th revised), 2023 Supplement. Left: water; right: salt equivalent. Karashi powder: water 4.9 g, salt equivalent 0.1 g. Prepared karashi: water 31.7 g, salt equivalent 7.4 g. Prepared mustard: water 65.7 g, salt equivalent 3.0 g. Whole-grain mustard: water 57.2 g, salt equivalent 4.1 g. Karashi powder contains almost no salt, but prepared karashi has a salt equivalent of 7.4 g per 100 g.Water and salt in four karashi and mustard products (per 100 g)Water (g)Salt equivalent (g)05010002468Karashi powderJapanese/Western typesKarashi powder 4.9g4.9Karashi powder 0.1g0.1Prepared karashiJapanese/Western stylesPrepared karashi 31.7g31.7Prepared karashi 7.4g7.4Prepared mustarda.k.a. French mustardPrepared mustard 65.7g65.7Prepared mustard 3.0g3.0Whole-grain mustarda.k.a. coarse-groundWhole-grain mustard 57.2g57.2Whole-grain mustard 4.1g4.1Karashi powder has almost no salt; tube karashi lists salt in its ingredients (e.g., the S&B Foods page).Source: MEXT Food Composition Tables (8th rev., 2023 Suppl.), food Nos. 17057–17060. Per 100 g edible portion.
Made from MEXT, Standard Tables of Food Composition in Japan (8th revised), 2023 Supplement (food Nos. 17057, 17058, 17059, 17060). Per 100 g of edible portion. Karashi powder includes both Japanese and Western karashi, and prepared karashi includes both Japanese-style and Western-style values.

In the Food Composition Tables (8th revised, 2023 Supplement), the salt equivalent per 100 g of karashi powder is 0.1 g, but it is 7.4 g for prepared karashi, 3.0 g for prepared mustard, and 4.1 g for whole-grain mustard. Converted to 5 g, that is about 0.4 g for prepared karashi and about 0.2 g for whole-grain mustard (calculated from the values in the Tables). Salt intake is covered in the article on salt intake.

Comparing How They Are Made and Their Ingredients

Type Main seed How it is made Examples of ingredient lists (manufacturers’ official and sales pages, checked October 2026)
Karashi powder (Japanese karashi) Brown (oriental type) Seeds are ground to a powder. Mix with water before use S&B Foods “漬物やおでんに合う辛さひきたつ和からし” (Japanese karashi with a heat that suits pickles and oden): mustard / S&B Foods “からし 35g” (can): mustard (Canada) / coloring (turmeric)
Tube prepared karashi Brown type Sold already mixed. Ingredients for storage and texture are often added S&B Foods “本生和からし” (Honnama Wa-Karashi): mustard (Canada), salt, dextrin, corn oil, starch / sorbitol, acidulant, flavoring, thickener (xanthan), antioxidant (vitamin C)
Yellow mustard (American style) White mustard White mustard mixed with vinegar and spices, often colored yellow with turmeric S&B Foods “マスタード（スクイズパック）” (Mustard, squeeze pack): mustard, brewed vinegar, salt, paprika, garlic / coloring (turmeric), thickener (xanthan)
Dijon mustard Only black or brown (French law) Seed coats are removed, ground, and mixed with vinegar, wine, etc. MAILLE “ディジョンマスタード” (Dijon Mustard) (S&B Foods): mustard, brewed vinegar, salt / acidulant, antioxidant (sulfites) / Biostar “有機ディジョンマスタード” (Organic Dijon Mustard): organic mustard, organic brewed vinegar, salt
Whole-grain mustard (old-fashioned) Only black or brown (French law) Coarsely ground with the coat (not sieved) MAILLE “種入りマスタード” (Seeded Mustard) (S&B Foods): brewed vinegar, mustard, salt, white wine, sugar / flavoring, acidulant, antioxidant (sulfites) / Tsuki no Amrita “粒マスタード” (Whole-Grain Mustard): mustard seeds, vinegar, white wine vinegar, sherry vinegar, salt
  • In Japanese ingredient lists, it is written “からし (karashi),” “マスタード (mustard),” or “マスタードシード (mustard seed)” regardless of the kind of seed. You cannot tell from the ingredient list which seed is used
  • Ingredients are listed in order of weight used, from the most. In MAILLE’s “種入りマスタード,” brewed vinegar comes first, and in Tsuki no Amrita’s whole-grain mustard, mustard seeds come first
  • “酸化防止剤（亜硫酸塩） (antioxidant (sulfites))” is a food additive also used in wine and dried fruit, and in the EU it is subject to allergen labeling (when it exceeds 10 mg per kg) (Additives database)
  • For “香料 (flavoring)” see the article on flavorings, and for sweet ingredients such as “ソルビット (sorbitol)” see the article on sweeteners

Japanese Karashi and Tube Karashi Paste

Karashi powder often has just “からし” (karashi) in its ingredient list, and you add water and mix it yourself. Tube karashi paste is ready to use, but in exchange it has added salt, starch, dextrin, vegetable oil, sorbitol, acidulant, flavoring, thickener, and the like.

Even among products called “karashi powder,” some use a coloring (turmeric) to make the color uniform and some are just karashi. A yellow color is not always “the color of karashi,” so checking the ingredient list is the sure way.

The “prepared karashi” in the Tables is a value that includes both Japanese-style and Western-style.

Dijon Mustard

France has a decree that sets how the names of mustard may be used (Decree No. 2000-658 of July 6, 2000). In it, the conditions for calling a mustard “Dijon mustard (moutarde de Dijon)” are as follows.

Condition Content
Seeds Only seeds of black mustard or brown mustard (white mustard may not be used). Seeds that have not had their oil pressed out
Coat The coat is removed by sieving. The remaining coat is up to 2% of the weight of the product
Richness of content Solids from the seed 22% or more, fat from the seed 8% or more
Mixing liquid Vinegar (fermented vinegar, wine vinegar, alcohol vinegar, cider vinegar), juice of unripe grapes (verjuice), grape juice, wine. Water is up to three quarters of the total liquid
Aroma Natural flavorings may be used, but mustard-flavored ones (such as allyl isothiocyanate) may not be added. Adding grain flour or coat is also prohibited

The conditions of this decree concern the seeds, coat, content, and liquid, and “made in the town of Dijon” is not among the conditions. It also says that mustard legally made in other EU countries may be sold in France. S&B Foods likewise explains that Dijon mustard is made by the “traditional Dijon method,” and that only products meeting detailed standards are called that.

In a study using brown seeds, even when made from the same seeds, with the Dijon-style process that removes the coat and makes it smooth, the amounts of sinigrin and the pungent compounds (isothiocyanates) changed more with processing than with the method that leaves the grains (Cools et al., 2018, abstract).

Whole-Grain Mustard

Whole-grain mustard is made by coarsely crushing the seeds with the coat, without making them fine. In the French decree, “old-fashioned mustard (moutarde à l’ancienne)” is only black or brown seeds, coarsely ground without sieving, with solids from the seed of 18% or more and fat of 5% or more.

S&B Foods explains that the seed coat has almost none of the enzyme that is the source of the heat, so whole-grain mustard (old type) that uses the coat has a milder flavor.

The ingredient lists of whole-grain mustards sold in Japan differ quite a lot by product.

  • Tsuki no Amrita (Regasalt Co., Ltd., Nihonbashi, Naniwa Ward, Osaka)’s whole-grain mustard has an ingredient list of five items: “mustard seeds, vinegar, white wine vinegar, sherry vinegar, salt.” No sugar or additives are listed. The content is “1 jar” with no gram amount shown, and we could not find a mail-order sale by the maker. It is sold in-store at Michi-no-Eki Izumi Yama-ai no Sato (Izumi City, Osaka)
  • MAILLE’s “種入りマスタード” (Seeded Mustard) has brewed vinegar, mustard, salt, white wine, and sugar, plus flavoring, acidulant, and antioxidant (sulfites)
  • S&B Foods’ tube “つぶ入りマスタード” (Mustard with Grains) has mustard, concentrated apple juice, brewed vinegar, corn oil, salt, and honey, plus sorbitol, acidulant, and thickener

Yellow Mustard

The American-style yellow mustard used on hot dogs is said to be mostly white mustard seed mixed with vinegar and spices and colored with turmeric (Lietzow et al., 2021). The Health Canada assessment also says that white mustard seed is larger than brown, much less hot, and the main ingredient of North American-style mustard. The pungent compound of white mustard is not volatile, so the heat that hits the nose is not strong.

Among products sold in Japan, the ingredient list of S&B Foods’ “マスタード（スクイズパック）” (Mustard, squeeze pack) has mustard, brewed vinegar, salt, paprika, and garlic, plus a coloring (turmeric) and a thickener (xanthan).

Mustard Allergy

What Kind of Allergy Is It?

Mustard allergy is a food allergy in which the body’s immune system reacts to proteins in mustard seed. It is separate from the irritation caused by the pungent compound (allyl isothiocyanate).

  • The main causative proteins are “Sin a 1” of white mustard and “Bra j 1” of brown mustard. Both are a type called “2S albumin” and are very similar in shape, so a person who reacts to one kind of mustard is likely to react to other kinds as well (Health Canada assessment)
  • Sin a 1 is a protein that resists heat and is hard to break down even with digestive enzymes (such as trypsin). Mustard allergens are said to resist heat and processing (Health Canada assessment; Løvik et al., 2005)
  • The amounts that caused symptoms were very small. In a trial in French children, there were cases with symptoms at 40 mg of mustard condiment (equivalent to 13.5 mg of mustard seed and about 0.8 mg of protein) (Morisset et al., 2003, as introduced in the Health Canada assessment)
  • A reaction in a skin test or blood test does not always mean symptoms from actually eating it. In France, when 30 people aged 3 to 20 who reacted to mustard were given a challenge by eating it, 7 (23%) had symptoms. The authors say that removal should not be advised on the basis of tests alone and that a challenge by eating is needed to confirm (Morisset et al., 2003)
  • In a study in Spain of 38 mostly adult people with mustard allergy, 10.5% had experienced systemic anaphylaxis, and 97.4% also reacted to mugwort pollen. Many also reacted (were sensitized) to other Brassica plants, nuts, beans, and fruits of the rose family, and the authors propose a “mustard-mugwort syndrome” (Figueroa et al., 2005)

Numbers by Country and Survey

How common mustard allergy is differs greatly by country and by survey method.

Share of causative foods of food allergy among French children and in JapanTop (France): causes in 544 children with food allergy confirmed by oral food challenge (Rancé et al., 1999, abstract). Egg 36%, peanut 24%, cow’s milk 8%, mustard 6%, cod 4%. Bottom (Japan): causes in 6,033 cases of immediate-type food allergy seen at medical institutions in 2023 (Consumer Affairs Agency fiscal 2024 report, Table 7-1). Egg 26.7%, walnut 15.2%, cow’s milk 13.4%, wheat 8.1%, peanut 7.0%. Mustard was 1 case (about 0.02%). The surveys differ in population, age, and diagnosis, so the numbers cannot be compared directly.Share of mustard among the causes of food allergyThe two surveys differ in population, age, and diagnosis, so the numbers cannot be compared directlyFrench children (published 1999)544 children confirmed by food challenge; top 5 foods0%10%20%30%40%EggEgg 36%36%PeanutPeanut 24%24%Cow’s milkCow’s milk 8%8%MustardMustard 6%6%CodCod 4%4%Japan (2023 national survey)6,033 immediate-type cases; top 5 foods and mustard0%10%20%30%40%EggEgg 26.7%26.7%WalnutWalnut 15.2%15.2%Cow’s milkCow’s milk 13.4%13.4%WheatWheat 8.1%8.1%PeanutPeanut 7.0%7.0%MustardMustard 1 case (about 0.02%)1 case (about 0.02%)Sources: Rancé F et al. Pediatr Allergy Immunol 1999 (PMID 10410915, abstract) /Consumer Affairs Agency, fiscal 2024 report of the research project on food labeling related to food allergies,nationwide survey of health damage caused by immediate-type food allergy, Table 7-1
France: Rancé et al. (1999, abstract). Share of causes among 544 children with food allergy confirmed by a challenge by eating. Japan: Consumer Affairs Agency, “Fiscal 2024 Report of the Research Project on Food Labeling Related to Food Allergies,” Table 7-1 (6,033 immediate-type cases reported for 2023). The surveys differ in population, age, and diagnostic method, so they cannot be compared directly.
Country or region Survey Result
France 544 children with food allergy confirmed by a challenge by eating (Rancé et al., 1999) 6% of causes were mustard, 4th after egg, peanut, and milk
France Background statement in a research paper (Morisset et al., 2003) 1.1% of food allergy in children
German-speaking countries Registry of anaphylaxis (severe allergic reaction) (Worm et al., 2016) Mustard is a “rare cause”
US Case report of anaphylaxis in a child under 2 (Katz et al., 2026) Points out that it is a cause not well known in the US and that there is no labeling requirement
Japan 6,033 cases of immediate-type food allergy seen at medical institutions in 2023 (Consumer Affairs Agency, fiscal 2024 report) Mustard was 1 case

(The French studies targeted children who came to specialist allergy facilities, and the numbers are not shares of the whole country. The Japanese survey consists of cases that were reported by cooperating doctors, of people who developed symptoms within 60 minutes of eating and were seen by a doctor.)

Labeling Rules Differ by Country

Country or region Labeling of mustard Rule
EU Mandatory One of the 14 items in Annex II of the Food Information Regulation (1169/2011): “mustard and products thereof.” In the ingredient list, it is emphasized in a way that sets it apart from the rest, such as bold type
UK Mandatory The same 14 items as the EU
Switzerland Mandatory One of the 14 items
Canada Mandatory One of the 11 “priority allergens.” A regulatory amendment was published in February 2011, giving businesses an 18-month preparation period, and applies from 2012. Health Canada decided to add it after a public consultation in 2008 and a scientific assessment
US Not covered The major allergens are the 9 items of milk, egg, fish, crustacean shellfish, tree nuts, wheat, peanuts, soybeans, and sesame (sesame from January 2023)
Japan Not covered Not in either the 9 mandatory “specified ingredients” (shrimp, crab, walnuts, wheat, buckwheat, egg, milk, peanuts, cashew nuts) or the 19 recommended “items equivalent to specified ingredients” (as of April 2026)
Australia and New Zealand, South Korea, China Not covered According to a survey commissioned by the Consumer Affairs Agency (fiscal 2023)

What to Watch for on Japanese Labels

In Japan, mustard is not subject to allergen labeling, so it does not appear in the “allergens” field of the label. For example, on the sales page of the organic Dijon mustard introduced above, only “wheat” is listed as an allergen.

In addition, under Japan’s Food Labeling Standards, if the total weight of spices is 2% or less of all ingredients, they may be written together as “香辛料 (spices)” or “混合香辛料 (mixed spices)”. The Consumer Affairs Agency’s Q&A gives an example of mustard (0.3%) in a retort curry being grouped into “other spices.” In the “spices” of curry, sauces, dressings, sausages, and the like, mustard may be included without being named.

For people with mustard allergy, in addition to checking whether “からし” or “マスタード” is in the ingredient list, the sure way is to ask the manufacturer about products that say “香辛料.” As foods that may contain mustard, an overseas review lists barbecue sauce, curry sauce, ketchup, mayonnaise, dressings, processed meats such as sausages, and flour for coating fried foods.

Summary

Point What is known Strength of evidence
Seed types Three kinds: white mustard, brown (mustard greens), and black mustard. Japanese karashi is the brown type Review, manufacturer’s explanation, Health Canada
Mechanism of the heat When water gets in, myrosinase works: sinigrin → allyl isothiocyanate (sharp), sinalbin → 4-hydroxybenzyl isothiocyanate (mild) Review, experimental papers
Boiling water and vinegar The enzyme works less well with heat and acid. The manufacturer’s instructions are to dissolve in lukewarm water of about 40°C and leave for 4 to 5 minutes Test-tube experiments, enzyme database, manufacturer’s instructions
Dijon and whole-grain Under French decree, Dijon is only black or brown seeds with the coat removed, and old-fashioned (whole-grain) is coarsely ground with the coat Law
Ingredient list Karashi powder may be just “からし.” Tubes have salt, starch, oil, sorbitol, acidulant, flavoring, etc. Some Dijon contains sulfites Manufacturers’ official labels
Salt Per 100 g: karashi powder 0.1 g, prepared karashi 7.4 g, prepared mustard 3.0 g, whole-grain mustard 4.1 g Food Composition Tables
Allergen labeling Mandatory in the EU, UK, Switzerland, and Canada; not covered in Japan or the US. In Japan it may be written together as “香辛料” Laws, Consumer Affairs Agency documents
How common 6% of causes in a French children’s study. 1 case out of 6,033 in Japan’s 2023 national survey Observational study, national survey (methods differ and cannot be compared)

Products featured:

Product Why we chose it Rakuten Ichiba
山清 有機 鬼からし 30g (Yamasei Organic Oni-Karashi, 30 g) The ingredient list is only organic karashi. You can mix it yourself and check the heat See on Rakuten (ナチュルネスパ) PR
See on Amazon.co.jp PR
See on Yahoo! Shopping PR
ビオスター 有機ディジョンマスタード 200g (Biostar Organic Dijon Mustard, 200 g) Three items: organic mustard, organic brewed vinegar, and salt. No sulfites listed See on Rakuten (楽天24) PR
See on Amazon.co.jp PR
See on Yahoo! Shopping PR
ビオスター 有機粒マスタード 200g (Biostar Organic Whole-Grain Mustard, 200 g) Three items: organic mustard, organic brewed vinegar, and salt. No sugar listed See on Rakuten (楽天24) PR
See on Amazon.co.jp PR
See on Yahoo! Shopping PR
月のアムリタ 粒マスタード (Tsuki no Amrita Whole-Grain Mustard) Mustard seeds, three kinds of vinegar, and salt. No sugar or additives listed Not sold by mail order (in-store at Michi-no-Eki Izumi Yama-ai no Sato)

(Prices and ingredients were checked on the sales pages on October 1, 2026. They may change.)

Mustards line up on the same shelf as “hot condiments,” but the heat and the contents differ by the kind of seed, how it is mixed, and the liquid added. Check the ingredient list on the back label to see what is in it.

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This article organizes labeling rules and evaluations based on public agencies' documents and research. It does not judge whether any particular food or additive is safe or dangerous. Rules in Japan and abroad change over time (checked 2026-10-01). This is a translation of our Japanese article; if they differ, the Japanese article is the reference.