Rooibos and Histamine – What Do We Know About Tolerance?
What happens when green and red rooibos are processed – and why “fermented” does not automatically mean “high in histamine”.
At a glance
Is rooibos suitable for people with histamine intolerance? The Swiss Interest Group Histamine Intolerance (SIGHI) classifies pure, unflavoured rooibos tea as generally well tolerated. This is a useful guide for people affected by histamine intolerance. It does not, however, mean that every batch of rooibos has been laboratory-tested and found to contain zero histamine, or that everyone will tolerate rooibos equally well.
Another question often causes confusion: Why is red rooibos described as “fermented”, while green rooibos is called “unfermented”? Does this difference also mean more histamine? The answer becomes clearer when we distinguish three separate processes.
Histamine in food
Under suitable conditions, it can be produced through the metabolism of certain microorganisms.
Oxidation in rooibos
Changes plant compounds and gives red rooibos its reddish-brown colour – a different chemical process.
Histamine in the body
Is released by mast cells, among others, and has normal physiological functions.
Understanding the science
How is rooibos classified on histamine tolerance lists?
The SIGHI food compatibility list gives pure rooibos tea a score of 0, meaning that it is generally considered well tolerated. The list also points out that products sold as rooibos may be tea blends containing additional ingredients that some individuals find problematic.
An important distinction: A SIGHI score of 0 is a tolerance rating, not a laboratory result showing 0 mg of histamine. Nor does it guarantee an identical histamine content across every harvest, producer or product.
For anyone looking specifically for rooibos tea, it is therefore important to distinguish between pure rooibos and rooibos blends. The product's ingredient list shows what it contains.
How does histamine form in food?
Histamine is a biogenic amine. During food production, it can form when certain microorganisms use an enzyme called histidine decarboxylase to convert the amino acid histidine into histamine. This process can be relevant, for example, in protein-rich foods that have been stored improperly or in certain types of microbial maturation.
However, several conditions must coincide for histamine to form: sufficient accessible starting material, the relevant microorganisms and suitable environmental conditions. Moisture, temperature, time and hygienic handling all play a part. Simply storing or drying a food, or describing it as “fermented”, does not by itself make it high in histamine.
Water availability also matters. The less water is available to microorganisms, the more their further growth is generally restricted. Histamine that has already formed, however, is not reliably removed by drying or ordinary heating.
Why does “fermented” red rooibos not necessarily contain more histamine?
Because traditional rooibos “fermentation” is primarily the oxidation of plant compounds. After the plant material has been cut and handled, polyphenols in particular undergo reactions involving enzymes naturally present in the plant. This is how red rooibos develops its characteristic reddish-brown colour and distinctive flavour profile.
Microbial histamine formation, by contrast, involves a completely different reaction: microorganisms convert histidine into histamine. The reddish colour of rooibos is therefore not, in itself, evidence that histamine has formed.
| Feature | Green rooibos | Red rooibos |
|---|---|---|
| Processing principle | Extensive oxidation is limited as far as possible. | Oxidation of plant compounds is deliberately allowed to proceed. |
| Drying | Takes place promptly to limit further oxidation. | Follows the traditional oxidation stage. |
| Is oxidation itself the formation of histamine? | No. | No. |
| Can processing tell us the exact histamine content? | No. | No. |
| Is either type demonstrably better tolerated overall? | Reliable direct studies are lacking for such a general comparison. | |
The term “fermented” has a long history in rooibos production and remains common in food processing terminology. It can nevertheless be misleading if it is equated with microbial fermentation, as occurs in some other foods.
Is green rooibos therefore a better choice for histamine intolerance?
Current scientific evidence does not support such a general conclusion. Green rooibos is dried more quickly to limit oxidation as far as possible. This may also shorten the period during which moist plant material offers favourable conditions for microbial growth. But it does not automatically follow that green rooibos contains less histamine than red rooibos.
A reliable answer would require measured histamine concentrations in comparable batches of green and red rooibos, taking account of the raw material, processing and storage. We did not find representative direct comparisons of this kind in the research reviewed.
An example from production: Skimmelberg describes a short processing sequence for its green rooibos: harvesting in the morning, followed by cutting and spreading out the material to dry, then collecting it within a few hours. This illustrates the aim of rapid processing, but it is not a histamine analysis of the product concerned.
For a closer look at how the two types differ in flavour, see our article “Green Rooibos – Aroma, Taste and Quality”.
Why does the human body produce histamine?
Histamine is not only a substance that we may consume in food. The human body produces it too. Among other functions, histamine acts as a signalling molecule in immune responses, the regulation of stomach acid and the nervous system. Certain immune cells – particularly mast cells – store histamine and can release it when activated.
In the intestine, the enzyme diamine oxidase (DAO) plays a major role in breaking down histamine taken in with food. Other pathways, including histamine N-methyltransferase (HNMT), also form part of the body's histamine metabolism. The picture is therefore more complex than the idea that every food containing histamine must necessarily cause symptoms.
The term “histamine intolerance” is used when discussing symptoms associated with food and histamine, but their causes are not always easy to establish. Medical guidelines stress that a single blood DAO measurement cannot provide a reliable diagnosis. A person's medical history and the assessment of other possible causes therefore matter.
Research & sources
What does research tell us about aspalathin and mast cells?
Two areas of research meet here, and they are often confused: histamine that may be present in a food and histamine released by the body's own cells.
A research group led by Kim studied the rooibos plant compound aspalathin in cell cultures and mouse models of allergic reactions. Under the experimental conditions, the researchers observed changes in mast-cell activation and histamine release. These studies concerned isolated aspalathin and particular experimental signalling pathways – not the consumption of ordinary rooibos tea by people with histamine intolerance.
The research question is: Can a plant compound influence cellular processes involving histamine? This can be investigated in the laboratory. It does not establish that drinking rooibos tea helps people with histamine intolerance.
Readers interested in aspalathin, polyphenols and their roles in plants can explore our article “Rooibos – Plant Compounds and Phytochemistry”. The findings from cell and animal experiments are discussed in our separate research overview.
What links rooibos, gut bacteria and biogenic amines?
Gut microorganisms also produce various metabolic substances, including certain biogenic amines. In a study by Pretorius and colleagues (2022), green and red rooibos extracts were added to selected microorganism cultures. The researchers observed changes in microbial growth and in the production of certain amines, including putrescine and tryptamine.
This study provides interesting indications that rooibos compounds may interact with microbial metabolism. It was, however, not a measurement of histamine in rooibos tea and does not demonstrate that rooibos affects histamine-related problems in humans. Distinguishing laboratory findings from everyday consumption is essential when interpreting research.
What should you look for when choosing rooibos tea?
Anyone considering rooibos because of possible histamine intolerance may find it helpful to distinguish three things:
- Pure rooibos or a blend? Pure products list rooibos as their only ingredient. Blends may contain other herbs, fruit, peel or flavourings.
- Processing and storage: Careful drying and dry storage are general markers of quality, partly because they limit conditions favourable to unwanted microbial activity.
- Individual response: A food compatibility list reflects typical experiences, not your own tolerance. If symptoms keep recurring, medical assessment is more useful than adopting an ever more restrictive list of foods to avoid.
If the precise histamine content of a particular product is the main concern, only a suitable product-specific laboratory analysis can answer that question – not its description as “green”, “red” or “fermented”.
What can we conclude about rooibos and histamine?
Pure rooibos tea is often classified as generally well tolerated. The term “fermentation”, commonly used for red rooibos, refers mainly to the oxidation of its plant compounds and is not evidence of an increased histamine content. Green rooibos is processed differently, but this does not automatically mean that it is histamine-free or generally better tolerated.
Research also explores other questions: How do microorganisms form biogenic amines, and how do mast cells respond to certain plant compounds? These questions make rooibos an interesting subject for research, provided we keep food composition, individual symptoms and laboratory findings clearly separate.
Sources and scientific studies
- SIGHI: Food compatibility list (German) – practical classification of pure rooibos and notes on blends.
- Allergieinformationsdienst: Histamine intolerance (German) – diagnostic questions and the limitations of individual laboratory measurements.
- Reese et al. (2021): Guideline on suspected adverse reactions to ingested histamine – assessment of symptoms and diagnostic approaches.
- Research on enzymatic oxidation in rooibos (2019) – the role of enzymes naturally present in the plant during so-called fermentation.
- Kim et al. (2024): Aspalathin and mast-cell activation – cell and mouse models, not a clinical rooibos study.
- Pretorius et al. (2022): Rooibos and biogenic amines in microbial cultures – experimental investigations of microbial growth and amine profiles.