Manzanilla, the Spanish word for chamomile, is one of the most ancient medicinal herbs known to mankind [1.8.4]. Utilized for millennia to aid with sleep, anxiety, and stomach ailments, it is most commonly consumed as an herbal tea made from the dried flowers of the plant [1.2.3, 1.8.4]. While generally considered safe for oral use in typical amounts, it's not without potential risks [1.2.1]. A deeper look into its pharmacological profile reveals specific side effects, interactions, and contraindications that users should be aware of.
Common and Mild Side Effects
Though uncommon, the most frequently reported side effects of manzanilla include drowsiness, nausea, and dizziness [1.2.1, 1.2.2]. Drowsiness is a primary effect, which is often a desired outcome for those using it as a sleep aid but can be a risk if consumed before activities requiring alertness, like driving [1.2.6]. High doses are more likely to induce nausea or even vomiting [1.2.2, 1.2.4]. When applied topically near the eyes, chamomile preparations can cause eye irritation [1.2.1].
Allergic Reactions: A Key Concern
The most significant risk associated with manzanilla is allergic reactions [1.5.1]. Individuals with known allergies to plants in the Asteraceae (or Compositae) family are at a higher risk [1.3.6]. This family includes:
- Ragweed
- Daisies
- Marigolds
- Chrysanthemums
- Sunflowers [1.5.2, 1.5.1]
Symptoms of an allergic reaction can range from mild skin rashes (contact dermatitis) and sneezing to severe, life-threatening anaphylaxis [1.2.2, 1.3.6]. Signs of a severe reaction require immediate medical attention and include difficulty breathing (asthma), swelling of the throat or lips (angioedema), and a widespread itchy rash [1.5.2].
Potential for Hormonal Effects
Some evidence suggests that chamomile may exhibit mild estrogenic effects [1.2.6]. This means it could potentially interfere with hormone-sensitive conditions. Individuals with a history of breast or uterine cancer or endometriosis should consult a healthcare provider before using manzanilla regularly [1.2.1, 1.2.6]. It has also been suggested that chamomile might decrease the effectiveness of estrogen-containing oral contraceptives [1.4.3].
Significant Drug Interactions
Manzanilla can interact with several types of prescription and over-the-counter medications. Its mild blood-thinning properties can increase the risk of bleeding when taken with anticoagulant or antiplatelet drugs [1.4.4]. It can also enhance the effects of sedatives, increasing drowsiness and other central nervous system effects [1.2.3].
Key medications that may interact with manzanilla include:
- Blood thinners: Warfarin (Coumaden), clopidogrel (Plavix), and even aspirin [1.4.4, 1.2.2].
- Sedatives: Benzodiazepines, barbiturates, drugs for insomnia, and alcohol [1.2.3, 1.2.2].
- Cyclosporine: A medication used to prevent organ transplant rejection [1.3.6, 1.4.2].
- Other supplements: Caution should be used when combining with other herbs that have similar effects, such as ginkgo biloba, garlic, and St. John's wort [1.4.5].
Anyone taking regular medication should speak with a doctor before using manzanilla supplements [1.2.2]. It is also recommended to stop taking chamomile at least two weeks before any scheduled surgery to reduce the risk of bleeding and potential interactions with anesthesia [1.7.1].
Herbal Tea Side Effect Comparison
| Feature | Manzanilla (Chamomile) | Peppermint Tea |
|---|---|---|
| Primary Use | Relaxation, Sleep, Anti-Anxiety [1.2.3] | Digestive Aid, Nausea Relief [1.9.3] |
| Common Side Effects | Drowsiness, Dizziness [1.2.1] | Heartburn, Nausea [1.9.1, 1.9.2] |
| Allergy Profile | Risk for those allergic to ragweed, daisies, marigolds [1.5.3] | Rare, but sensitivity to menthol can cause reactions [1.9.5] |
| Key Contraindication | People on blood thinners (e.g., Warfarin) [1.4.4] | People with GERD (Acid Reflux) [1.9.1, 1.9.4] |
| Pregnancy Advisory | Generally advised to avoid or use with caution due to lack of data and potential risks [1.6.5, 1.6.6] | Generally considered safe in moderation for nausea, but consultation is advised [1.9.5] |
Considerations for Special Populations
Pregnancy and Breastfeeding
There is limited and conflicting information on the safety of manzanilla during pregnancy and breastfeeding [1.2.1, 1.6.6]. Some studies have linked its use to a higher risk of preterm delivery and lower birth weight, leading many healthcare providers to recommend avoiding it, especially in large or medicinal amounts [1.6.5, 1.6.6]. While some sources state it may be safe in moderation while breastfeeding, the long-term effects on infants are not well known [1.6.1]. Due to the lack of conclusive safety data, pregnant and breastfeeding individuals should consult their doctor before use [1.6.6].
Children
Manzanilla has been traditionally used to treat colic and diarrhea in infants [1.6.2]. While it is generally considered safe for children in the short term, it is crucial to talk to a pediatrician before giving it to babies or children to ensure proper dosage and safety [1.2.2, 1.5.4]. One notable risk is that botulism spores have been found in some commercial loose-leaf chamomile preparations [1.6.2].
Conclusion
Manzanilla is a widely used herbal remedy with a long history and many perceived benefits. For most healthy adults, consuming it in tea form is likely safe [1.2.1]. However, the potential for side effects is real and deserves careful consideration. The most critical risks involve allergic reactions in susceptible individuals and dangerous interactions with medications like blood thinners and sedatives. Special populations, including pregnant women and those with hormone-sensitive conditions, should exercise particular caution. As with any supplement, consulting with a healthcare provider is the best way to ensure that using manzanilla is safe for your individual health circumstances.
For more information from an authoritative source, visit the National Center for Complementary and Integrative Health (NCCIH).
