Drug & supplement interaction

Barley + Letrozole

Letrozole brand name: Femara.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Barley and Letrozole in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first.

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Interaction report

Barley and Letrozole

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Letrozole and Barley in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Barley safety at a glance

Barley overall Generally safe Barley is safe for most people when eaten as a normal food, but it contains gluten.
Pregnancy Likely Safe When used orally in amounts commonly found in foods. Read the full pregnancy detail
Breastfeeding Use caution Barley as a food is considered fine, but there is little safety data on concentrated barley supplements while breastfeeding.

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Letrozole and Barley? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Letrozole

Interactions in our licensed database are recorded against drug classes, not just single drug names. Letrozole is filed under 4 classifications — including aromatase inhibitors, cytochrome p450 2c19 (cyp2c19) inhibitors, cytochrome p450 3a4 (cyp3a4) substrates. Barley has documented interactions with 1 drug class — the most serious being triclabendazole (egaten) (moderate) — and none of Letrozole’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Barley Does Interact With Other Medications

Barley has 1 moderate known drug interaction in our database — Letrozole isn’t one of them. If you take anything else, check it against the full list below.

Moderate 1 No known interaction 2,829 (incl. Letrozole)
Taking anything else?

Check Another of Your Medications Against Barley

Covers the 2,830 medications we’ve checked against Barley. Pick one to open its full report.

What to actually watch for

What Barley Itself Has Been Linked To

This is not an interaction — nothing below involves Letrozole. It is the side-effect record for Barley on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Barley, this list is the first place to look. 4 entries are worth acting on rather than waiting out — marked below.

  • Fainting / Chest pain / Shortness of breath / A severe allergic reaction Worth acting on Additional detail

    “Orally, consumption of beer has been reported to cause allergic reactions in sensitive individuals. Symptoms included tingling in the face, lip, and tongue, angioedema, generalized urticaria, chest tightness, dyspnea, cough, fainting, and rhinoconjunctivitis. It can also cause anaphylaxis in sensitive individuals.”

    Barley · Natural Medicines adverse-effect record, reported in asthma.

    6 sources cited
    1. 33722. Curioni, A., Santucci, B., Cristaudo, A., Canistraci, C., Pietravalle, M., Simonato, B., and Giannattasio, M. Urticaria from beer: an immediate hypersensitivity reaction due to a 10- kDa protein derived from barley. Clin Exp Allergy 1999;29(3):407-413. PubMed
    2. 33724. Fernandez-Anaya, S., Crespo, J. F., Rodriguez, J. R., Daroca, P., Carmona, E., Herraez, L., and Lopez-Rubio, A. Beer anaphylaxis. J Allergy Clin Immunol. 1999;103(5 Pt 1):959-960.
    3. 317. Fernandez-Anaya S, Crespo JF, Rodriguez JR, et al. Beer anaphylaxis. J Allergy Clin Immunol 1999;103:959-60.
    4. 33762. van Ketel, W. G. Immediate type allergy to malt in beer. Contact Dermatitis 1980;6(4):297-298. PubMed
    5. 33735. Cronin, E. Contact dermatitis from barley dust. Contact Dermatitis 1979;5(3):196. PubMed
    6. 33770. Gutgesell, C. and Fuchs, T. Contact urticaria from beer. Contact Dermatitis 1995;33(6):436-437. PubMed
  • Wheezing Worth acting on Additional detail

    “"Bakers' asthma" is an allergic response resulting from the inhalation of cereal flours by workers in the baking and milling industries, and has been reported to occur after barley flour exposure. Cross-allergenicity has been shown to exist between different cereals.

    By inhalation, barley flours may be a source of allergens in asthma.”

    Barley · Natural Medicines adverse-effect record, reported in asthma.

    3 sources cited
    1. 33758. Block, G., Tse, K. S., Kijek, K., Chan, H., and Chan-Yeung, M. Baker's asthma. Studies of the cross-antigenicity between different cereal grains. Clin Allergy 1984;14(2):177-185.
    2. 33764. Vidal, C. and Gonzalez-Quintela, A. Food-induced and occupational asthma due to barley flour. Ann Allergy Asthma Immunol. 1995;75(2):121-124.
    3. 33773. Nakase, M., Usui, Y., Alvarez-Nakase, A. M., Adachi, T., Urisu, A., Nakamura, R., Aoki, N., Kitajima, K., and Matsuda, T. Cereal allergens: rice-seed allergens with structural similarity to wheat and barley allergens. Allergy 1998;53(46 Suppl):55-57. PubMed
  • Hives Worth acting on Additional detail

    “Topically, barley malt contained in beer has been reported to cause contact dermatitis. After occupational exposure, barley has been reported to cause contact dermatitis of the eyelids and extremities, as well as contact urticaria.”

    Barley · Natural Medicines adverse-effect record, reported in dermatitis.

    4 sources cited
    1. 33762. van Ketel, W. G. Immediate type allergy to malt in beer. Contact Dermatitis 1980;6(4):297-298. PubMed
    2. 33735. Cronin, E. Contact dermatitis from barley dust. Contact Dermatitis 1979;5(3):196. PubMed
    3. 33770. Gutgesell, C. and Fuchs, T. Contact urticaria from beer. Contact Dermatitis 1995;33(6):436-437. PubMed
    4. 33774. Pereira, F., Rafael, M., and Lacerda, M. H. Contact dermatitis from barley. Contact Dermatitis 1998;39(5):261-262. PubMed
  • An allergic reaction Worth acting on Additional detail

    “Orally, barley is well tolerated.

    Most Common Adverse Effects:

    Orally: Abdominal distension, bloating, flatulence, unpleasant taste. Allergic reactions in sensitive individuals.

    Topically: Allergic reactions in sensitive individuals.”

    Barley · Natural Medicines adverse-effect record, reported in flatulence.

  • Bloating or gas Additional detail

    “When consumed orally, barley provides fiber. Increasing fiber in the diet can cause flatulence, bloating, abdominal distention, and unpleasant taste. To minimize side effects, doses should be slowly titrated to the desired level. Adverse effects usually subside with continued use.

    Barley contains gluten.”

    Barley · Natural Medicines adverse-effect record, reported in flatulence.

    3 sources cited
    1. 12514. Lembo A, Camilleri M. Chronic constipation. N Engl J Med 2003;349:1360-8. . PubMed
    2. 33763. Ellis, H. J., Doyle, A. P., Day, P., Wieser, H., and Ciclitira, P. J. Demonstration of the presence of coeliac-activating gliadin-like epitopes in malted barley. Int Arch Allergy Immunol. 1994;104(3):308-310. PubMed
    3. 33772. Baker, P. G. and Read, A. E. Oats and barley toxicity in coeliac patients. Postgrad.Med J 1976;52(607):264-268. PubMed
  • Numbness or tingling / Cough Additional detail

    Recorded for Barley in the same Natural Medicines adverse-effect record shown under Fainting / Chest pain / Shortness of breath / A severe allergic reaction above.

Showing the 10 most notable of 12 recorded effects — ranked by how unusual each one is across medicines generally, with serious effects weighted up.

Everything above comes from the Natural Medicines adverse-effect record for Barley — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Letrozole’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Letrozole column appears here.

Special populations

Barley in Pregnancy & Breastfeeding

Pregnancy Likely Safe

When used orally in amounts commonly found in foods.

Pregnancy Possibly Unsafe

When barley sprouts are consumed in relatively high doses. Excessive amounts of barley sprouts should not be consumed during pregnancy.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

From our Q&A

Questions About Barley or Letrozole

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Barley or Letrozole, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Letrozole

This page covers Barley only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Letrozole page lists 142 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), 7-methoxyflavone (moderate) and Acacia Rigidula (moderate).

By severity: 3 major · 99 moderate · 40 minor.

From our pharmacist’s overview on the Letrozole page

“Letrozole (Femara) is prescribed to keep hormone-driven breast cancer from returning, so a supplement that shifts its blood level can quietly undercut treatment. Give this list of 142 ingredients genuine respect, and learn the three major entries first.”

Reviewed by 2 · Jul 18, 2026

Open the Letrozole interaction page

One more smart check

Taking Barley as Part of a Dietary Supplement Product? Check It for Interactions

We hold 2,448 real supplement products containing Barley, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Barley. Even though Barley itself has no known interaction with Letrozole, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Barley and Letrozole Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Barley
Top 25%

#146 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Letrozole
Top 5%

#50 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Barley reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Barley and Letrozole records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Barley

What is Barley?

Barley
  • High cholesterol
  • Heart health support
  • Blood sugar support
  • Digestive regularity and fiber
  • General nutrition

Barley is a nutritious whole grain that is a good source of soluble fiber called beta-glucan, which has solid evidence for modestly lowering LDL ('bad') cholesterol when eaten regularly. It is safe as a food for most people, but those with celiac disease or gluten sensitivity should avoid it since it contains gluten. Talk to your pharmacist or doctor before using concentrated barley supplements, especially if you have a health condition.

Hordeum vulgare · Poaceae · Grain (seed), and sometimes young leaves/grass and bran · Whole grain, flour, flakes, barley bran, beta-glucan supplements, barley grass powder, tea, and capsules

An interaction check asks whether these two react with each other — it does not ask whether Barley is a good idea for someone in your situation. Here is what our Barley record says about it on its own.

Barley: dosing

There is no single official supplement dose for barley. For cholesterol benefits, research has generally used a few grams of barley beta-glucan per day, taken as part of the diet, but the exact amount can vary by product.Because products differ widely in strength and form, the best approach is to follow the directions on the product label.

From our Barley monograph — the full record covers uses, side effects and every documented interaction.

Read the full Barley monograph & all interactions
Medication

About Letrozole

What Is Letrozole Used For?

Brand name: Femara

Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer.

Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

See full Letrozole drug information
Keep checking

Other Drugs & Barley

Browse every other medication we’ve checked against Barley — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
1Moderate
0Minor
2,828No known interaction
1 Moderate 2,828 No interaction
Moderate

1 interaction

No interaction 2,828 drugs checked — show the list

We also checked Barley against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,828 medications checked with no known interaction — see the full Barley list.

See the full Barley interactions page
See every supplement checked against Letrozole, ranked by severity
Evidence & sources

Barley References

The 15 references that drive our Barley monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  2. Fernandez-Anaya S, Crespo JF, Rodriguez JR, et al. Beer anaphylaxis. J Allergy Clin Immunol 1999;103:959-60.
  3. Lembo A, Camilleri M. Chronic constipation. N Engl J Med 2003;349:1360-8. . PubMed
  4. Ferre, I., Giraldez, F. J., Alvarez-Bujidos, M. L., and Mantecon, A. R. Influence of barley supplement on plasma concentration of triclabendazole metabolites in sheep. Vet.Rec. 11-22-1997;141(21):549-551. PubMed
  5. Curioni, A., Santucci, B., Cristaudo, A., Canistraci, C., Pietravalle, M., Simonato, B., and Giannattasio, M. Urticaria from beer: an immediate hypersensitivity reaction due to a 10- kDa protein derived from barley. Clin Exp Allergy 1999;29(3):407-413. PubMed
  6. Fernandez-Anaya, S., Crespo, J. F., Rodriguez, J. R., Daroca, P., Carmona, E., Herraez, L., and Lopez-Rubio, A. Beer anaphylaxis. J Allergy Clin Immunol. 1999;103(5 Pt 1):959-960.
  7. Cronin, E. Contact dermatitis from barley dust. Contact Dermatitis 1979;5(3):196. PubMed
  8. Block, G., Tse, K. S., Kijek, K., Chan, H., and Chan-Yeung, M. Baker's asthma. Studies of the cross-antigenicity between different cereal grains. Clin Allergy 1984;14(2):177-185.
  9. van Ketel, W. G. Immediate type allergy to malt in beer. Contact Dermatitis 1980;6(4):297-298. PubMed
  10. Ellis, H. J., Doyle, A. P., Day, P., Wieser, H., and Ciclitira, P. J. Demonstration of the presence of coeliac-activating gliadin-like epitopes in malted barley. Int Arch Allergy Immunol. 1994;104(3):308-310. PubMed
  11. Vidal, C. and Gonzalez-Quintela, A. Food-induced and occupational asthma due to barley flour. Ann Allergy Asthma Immunol. 1995;75(2):121-124.
  12. Gutgesell, C. and Fuchs, T. Contact urticaria from beer. Contact Dermatitis 1995;33(6):436-437. PubMed
  13. Baker, P. G. and Read, A. E. Oats and barley toxicity in coeliac patients. Postgrad.Med J 1976;52(607):264-268. PubMed
  14. Nakase, M., Usui, Y., Alvarez-Nakase, A. M., Adachi, T., Urisu, A., Nakamura, R., Aoki, N., Kitajima, K., and Matsuda, T. Cereal allergens: rice-seed allergens with structural similarity to wheat and barley allergens. Allergy 1998;53(46 Suppl):55-57. PubMed
  15. Pereira, F., Rafael, M., and Lacerda, M. H. Contact dermatitis from barley. Contact Dermatitis 1998;39(5):261-262. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Barley and Letrozole Together: Common Questions

Is it safe to take Barley with Letrozole?
We do not list a known interaction between Barley and Letrozole. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
How was the Barley and Letrozole combination checked?
Interactions in our licensed database are recorded against drug classes. Letrozole is filed under 4 classifications, and Barley has documented interactions with 1 drug class — none of Letrozole's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Barley interact with any other medications?
Yes. Barley has 1 documented drug interaction in our database — Letrozole is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Letrozole interact with any supplements?
Yes. Letrozole has documented interactions with 142 supplements in our database — Barley is not one of them. The Letrozole interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

Barley monograph Uses, safety profile, and every drug interaction in one place Letrozole drug information The full plain-English guide to this medication Letrozole supplement interactions Every supplement checked against Letrozole, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 15 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Letrozole and Barley?

Our pharmacists answer your medication & supplement questions — free.

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.