Who Should Avoid Basil and Why

December 12, 2025 •

3 min read

An estimated 96.5% of people in a recent survey reported no adverse effects from consuming basil in food quantities, but for certain individuals, it poses significant health risks due to its potent compounds. Understanding who should avoid basil is crucial, especially when considering higher, medicinal doses or specific health conditions.

Quick Summary

An overview of who should limit or avoid basil, including individuals with bleeding disorders, those on specific medications like blood thinners or blood pressure drugs, and pregnant or breastfeeding women. Discusses the risks associated with high, medicinal doses versus standard culinary use.

Key Points

Blood Thinners: Individuals on anticoagulant or antiplatelet medications should avoid medicinal basil due to the risk of increased bleeding.
Pregnancy and Breastfeeding: It is advised to avoid large, medicinal doses of basil due to the presence of estragole, which may be harmful in high concentrations.
Surgery Prep: Anyone scheduled for surgery should stop using basil extracts at least two weeks prior to reduce the risk of excessive bleeding.
Low Blood Pressure: People with hypotension or those on blood pressure medication should be cautious, as basil extracts can further lower blood pressure.
Culinary vs. Medicinal: The risks are associated with high, concentrated doses in supplements or oils, not the small amounts typically used in cooking.
Holy Basil Differences: Holy basil (Tulsi) has specific contraindications related to thyroid function and fertility, distinct from sweet basil.
Consult a Doctor: Always talk to a healthcare professional before incorporating large amounts of basil into your diet, especially if you have an existing health condition or take medication.

Understanding Basil's Potent Compounds

While basil is a beloved herb in many cuisines, its leaves and oils contain compounds that can have powerful effects on the body, especially when consumed in concentrated forms. The main concerns stem from a chemical called estragole, which in high doses has been linked to potential health risks. Additionally, basil extracts and oils can influence blood pressure and blood clotting, making it a point of caution for certain populations. Standard culinary use, where only small amounts are consumed, is generally considered safe for most people, but the risks amplify with medicinal amounts found in supplements, tinctures, or essential oils.

Populations That Should Limit or Avoid Basil

It's important for individuals with specific health conditions or life stages to be aware of the potential risks associated with higher doses of basil.

Individuals on Blood-Thinning Medication: Basil extracts and oils may slow blood clotting. For those taking anticoagulant or antiplatelet drugs like warfarin (Coumadin), clopidogrel (Plavix), or aspirin, this could increase the risk of bruising and bleeding. This interaction makes it critical to moderate basil intake and consult a doctor before using any basil supplements.
People with Bleeding Disorders: Due to its potential to slow blood clotting, basil oils and extracts can worsen bleeding disorders. This includes conditions such as hemophilia or von Willebrand disease.
Patients Undergoing Surgery: Because of its blood-clotting effects, it is recommended to stop using medicinal amounts of basil at least two weeks before any scheduled surgical procedure.
Pregnant and Breastfeeding Women: While culinary amounts are likely safe, larger medicinal quantities of basil are considered possibly unsafe for both pregnant and breastfeeding women. Basil contains estragole, a chemical that has been linked to liver cancer in laboratory mice. Additionally, some animal studies suggest holy basil supplements may negatively affect sperm and trigger contractions, though more research is needed in humans. Always consult a healthcare provider before using basil medicinally during this time.
People with Low Blood Pressure: Basil extracts can lower blood pressure. For individuals already taking medication for high blood pressure, combining it with basil extracts could cause blood pressure to drop too low.

Comparison: Holy Basil vs. Sweet Basil

It is important to note the difference in effects and warnings between holy basil (tulsi) and sweet basil (Ocimum basilicum), though both require caution in concentrated forms.


Feature	Sweet Basil (Ocimum basilicum)	Holy Basil (Ocimum tenuiflorum / Tulsi)
Primary Compound of Concern	Estragole	Eugenol, estragole
Effect on Blood Clotting	Extracts and oils may slow clotting.	May slow blood clotting.
Effect on Blood Pressure	Extracts may lower blood pressure.	May help lower blood pressure.
Pregnancy/Breastfeeding Safety	Medicinal amounts possibly unsafe due to estragole.	Medicinal amounts possibly unsafe due to reproductive effects seen in animal studies.
Additional Considerations	Generally safe in culinary amounts.	Can affect thyroid hormone levels, worsening hypothyroidism.

Safe Culinary Use vs. Medicinal Doses

For most people, enjoying basil as a seasoning in pesto, sauces, or salads is perfectly safe and can even offer health benefits like antioxidants and vitamin K. The key distinction lies in the concentration. The risks discussed arise primarily from large, medicinal doses or in concentrated forms like extracts and essential oils. These are the situations where the active compounds are most potent and likely to cause adverse effects or interact with medications.

What to Do If You Have Concerns

If you have a health condition, are taking medication, or are pregnant, and are concerned about your basil intake, the first step is to consult your doctor or a qualified healthcare provider. They can provide personalized advice based on your medical history and specific situation. For those who frequently use large amounts of basil, perhaps in fresh juices or supplements, it is particularly important to have this conversation. If you notice any unusual symptoms after consuming basil, such as increased bleeding, dizziness, or changes in blood sugar, seek medical attention immediately.

Conclusion

While basil is a safe and healthy herb for the majority of the population when used in standard culinary amounts, certain individuals must approach it with caution. Those on blood thinners, pregnant or breastfeeding women, people with bleeding disorders, or those undergoing surgery are among those who should avoid or strictly limit their intake of medicinal basil extracts and essential oils. Always prioritize medical advice and err on the side of caution when in doubt regarding herbal supplements, especially when managing existing health conditions..

Frequently Asked Questions

You should be cautious. While small culinary amounts are usually fine, large medicinal doses, extracts, or essential oils of basil can slow blood clotting and interfere with blood-thinning medications like warfarin. Always consult your doctor for personalized guidance.

Regular culinary amounts of basil are generally considered safe. However, large, medicinal quantities or concentrated extracts are possibly unsafe due to the presence of estragole, a compound linked to potential risks in high doses. It is best to consult with a healthcare provider.

Yes, basil extracts have been shown to lower blood pressure. If you are taking medication for high blood pressure, combining it with basil extracts could cause your blood pressure to drop too low. Monitor your blood pressure closely and discuss it with your doctor.

In addition to the general precautions for basil, holy basil (Tulsi) should be avoided by pregnant or breastfeeding women in medicinal amounts and people with hypothyroidism, as it can decrease thyroid hormone levels. Consult a doctor, especially if taking thyroid medication.

Yes, if you consume basil in medicinal amounts (extracts or essential oils), you should stop at least two weeks before a scheduled surgery. Basil can slow blood clotting, which may increase the risk of bleeding during and after the procedure.

Basil is safe for children in small amounts used for cooking. However, large, medicinal amounts of basil are possibly unsafe due to the estragole content and should be avoided. Always prioritize the advice of a pediatrician for supplement use.

Basil allergies are rare, but they do occur. If you experience symptoms like itching, redness, or swelling after consuming basil, you may have a plant-based allergy and should seek medical advice.