Fermented Foods Safety: Histamine, Sodium, Listeria, Alcohol and Home Fermenting
Safety points for fermented foods in plain language: listeria, histamine and tyramine, salt, alcohol in kombucha, home fermenting, and who should ask a clinician first.
Content last updated . This page has not been medically reviewed.
Urgent first
Fermented foods are usually safe when properly made, but contaminated food can cause serious illness. The NHS says listeriosis can lead to sepsis or meningitis in babies and in people with a weakened immune system. [1] It lists a severe headache with a stiff neck among signs needing emergency help. [1] In the US, call 911 for an emergency. Pregnant women, people with a weakened immune system and anyone with severe or bloody diarrhea, fever or dehydration should seek medical care promptly rather than waiting. This page is information only, not medical advice.The general picture
When properly made from safe and wholesome ingredients, fermented foods are rarely associated with gastroenteritis, according to an ISAPP expert panel. [2] The same panel said some cheeses and low-acid fermented foods can pose a safety risk if contaminated with Listeria monocytogenes. [2] Its other cautions were alcohol, salt and biogenic amines such as histamine. [2]Safety points by topic
| Topic | What the sources say | Who should be careful |
|---|---|---|
| Listeria | Unpasteurised or soft-ripened dairy foods may contain listeria, which can cause listeriosis. [3] The FDA says pregnant women, the elderly and people with weakened immune systems should not eat unpasteurized milk products. [4] | Pregnancy; newborns; weakened immune system |
| Histamine and other amines | Histamine, tyramine and other biogenic amines are formed by some lactic acid bacteria from amino acids [2] during the fermentation of cheese, meats, vegetables, soybeans and wine. [2] These amines can cause mild to more severe effects such as migraines. [2] | People who react to these foods; people on certain medicines |
| Salt | Salt, for example in soy sauce or kimchi, is inherent in some fermented foods and should be consumed in moderation. [2] | High blood pressure; kidney conditions; babies and children |
| Alcohol | Alcohol is inherent in some fermented foods and drinks and should be consumed in moderation. [2] | Anyone who must avoid alcohol |
| Home fermenting | Do not cut back the salt in tested recipes for sauerkraut or fermented pickles. [5] | Anyone fermenting at home |
Histamine, tyramine and medicines
A review of histamine intolerance describes it as an impaired ability to metabolize ingested histamine, and said more scientific evidence is still required to define, diagnose and clinically manage it. [6] Proper evidence not found: we searched the ISAPP statement and the histamine review for a tested list of fermented foods that are safe for people who think they are sensitive. Neither gives one, so we do not list foods.Tyramine matters for people on certain medicines. MedlinePlus says people taking tranylcypromine may have a serious reaction if they eat foods high in tyramine. [7] It names yeast products that have fermented among the sources. [7] Never stop or change a prescribed medicine on your own. Ask your pharmacist about diet and see medication interactions.
Salt: official figures
| Group | Amount | Source and year |
|---|---|---|
| Adults (UK) | No more than 6 g salt a day (about 1 level teaspoon) [8] | NHS, page reviewed 2023 |
| Babies under 1 year (UK) | Less than 1 g a day [8] | NHS, page reviewed 2023 |
The NHS says eating too much salt can cause high blood pressure, and that babies should not have much salt because their kidneys are not fully developed. [8] We did not read a food-composition source for the salt in specific fermented foods, so we give no per-serving figures. Check the label.
Kombucha
- Case reports. A 2003 systematic review found no clinical efficacy studies, but several case reports and case series raised doubts about safety, including suspected liver damage, metabolic acidosis and cutaneous anthrax infections. [9] Case reports cannot prove cause, and the review is old. A 2019 review found only one empirical human study. [10]
- Alcohol content. Kombucha contains some alcohol from fermentation. In a New Zealand study of nine commercial samples, [11] 22% exceeded the 1.15% alcohol by volume threshold for non-alcoholic beverages. [11] In a Brazilian study of 30 brands, all labelled with up to 0.5% alcohol, [12] 60% of samples exceeded that limit, with levels from 0.10% to 1.70%. [12] These are two country studies, not all products.
- Home brewing. A USDA-based home-preservation guide says not to make kombucha with starter liquid whose pH is greater than 4.0. [13] It warns that airtight storage can lead to carbonation build-up and explosion. [13] It says to refrigerate promptly and use within 30 days. [13] Follow tested recipes only. [5]
Who should ask a clinician or pharmacist first
- Pregnancy and breastfeeding: unpasteurised dairy; see pregnancy and breastfeeding.
- Weakened immune system, cancer treatment, kidney or liver disease, diabetes: the NHS lists these among conditions with a higher risk of serious listeriosis. [1] NCCIH also says the risk of harm from probiotics is greater with severe illness or compromised immune systems. [14]
- Surgery: the sources we read do not address fermented foods before surgery. Ask your surgical team.
- Children: keep salt in mind (table above) and ask a pediatrician about unpasteurized foods.
For probiotic supplements see probiotic safety. To compare food and supplement, see fermented foods vs probiotic supplements. For side effects like gas, see probiotic side effects.
Official intake levels
The sources we read give salt limits (above) but no official recommended intake for fermented foods themselves.Frequently asked questions
Is it safe to eat fermented foods when pregnant?
Take care with unpasteurised dairy: the NHS says it may contain listeria, which can cause miscarriage or stillbirth. [3] Ask your midwife or doctor about specific foods.
Do fermented foods contain histamine?
ISAPP says some lactic acid bacteria form histamine and tyramine during fermentation of foods such as cheese, vegetables and soybeans. [2]
Can I cut the salt when I ferment vegetables at home?
Not in a tested recipe: a USDA-based guide says not to make sauerkraut or fermented pickles by cutting back on the salt required. [5]
Is kombucha safe?
Case reports raised doubts about safety in a 2003 review, and recent studies found alcohol above stated limits in some products. [9][11] People who need to avoid alcohol should ask a clinician.
What if I take an MAO inhibitor?
MedlinePlus says high-tyramine foods can cause a serious reaction with tranylcypromine. [7] Ask your pharmacist, and do not stop the medicine yourself.
References
- NHS (UK). Listeriosis. Page last reviewed 10 November 2023. Read 2026-10-23.
- Marco ML et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nat Rev Gastroenterol Hepatol 2021;18:196-208 (PMID 33398112). Read 2026-10-23.
- NHS (UK). Foods to avoid in pregnancy. Page last reviewed 15 June 2026. Read 2026-10-23.
- US Food and Drug Administration. Listeria (Listeriosis). Content current as of 16 January 2025. Read 2026-10-23.
- National Center for Home Food Preservation (University of Georgia; adapted from USDA Complete Guide to Home Canning, 2015). General information on fermenting. Read 2026-10-23.
- Comas-Basté O et al. Histamine intolerance: the current state of the art. Biomolecules 2020 (PMID 32824107). Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Tranylcypromine. Last revised 15 May 2017. Read 2026-10-23.
- NHS (UK). Salt in your diet. Page last reviewed 17 April 2023. Read 2026-10-23.
- Ernst E. Kombucha: a systematic review of the clinical evidence. Forsch Komplementarmed Klass Naturheilkd 2003 (PMID 12808367). Read 2026-10-23.
- Kapp JM, Sumner W. Kombucha: a systematic review of the empirical evidence of human health benefit. Ann Epidemiol 2019 (PMID 30527803). Read 2026-10-23.
- Comparing Alcolyzer and GC-FID for ethanol measurement in kombucha: insights from nutritional labeling and brewer practices in New Zealand. J Food Sci 2026 (PMID 41536259). Read 2026-10-23.
- Simultaneous quantification of alcoholic content and acidity in Brazilian commercial kombuchas by FTIR spectroscopy and chemometric analysis. J Food Sci 2025 (PMID 40754655). Read 2026-10-23.
- National Center for Home Food Preservation (University of Georgia). Kombucha tea. Read 2026-10-23.
- NCCIH (US National Center for Complementary and Integrative Health). Probiotics: Usefulness and Safety. Read 2026-10-23.