While peppermint has proven to be a therapeutically valuable aromatic plant, precautions need be taken to ensure the safe use of its oil.
- Unless included as a minor percentage in a professionally formulated blend, avoid use on children under 30 months of age. The nasal mucosa is an autonomic reflexogen organ, which has a distance action to the heart, lungs and circulation and may lead to sudden apnoea and glottal constriction.
- Peppermint oil should not be applied to the faces of infants and children due to the risk of apnea, laryngeal and bronchial spasms, acute respiratory distress with cyanosis and respiratory arrest. Except when included as a minor percentage in a professionally formulated blend, application of peppermint oil to the chest of infants should also be avoided.
- Do not apply undiluted peppermint essential oils to the feet, particularly on infants and children under the age of 12.
- Inhalation of large doses of menthol may lead to dizziness, confusion, muscle weakness, nausea and double vision. Avoid diffusing pure peppermint oil near infants and children. Diffuser blends intended for infants and children should include only a minor percentage of peppermint oil and should be used in a well ventilated room.
- Peppermint essential oil intended for oral use should always be appropriately diluted or enteric-coated in a tablet or capsule professionally formulated for internal use. The indiscriminate oral use of peppermint may cause heartburn, perianal burning, blurred vision, nausea and vomiting. Heartburn is related with the release of the oil in the upper GI tract, which relaxes the lower oesophageal sphincter, facilitating the reflux. The same occurs in the cases of hiatal hernia. This particular undesirable effect is minimized by an appropriate pharmaceutical formulation or dietary supplement.
- Patients with gallbladder disease, severe liver damage, gallstones and chronic heartburn should avoid the intake of peppermint oil except when used in highly diluted form under the guidance of a qualified health professional.
- Pure menthol and peppermint oil may cause burning mouth syndrome, recurrent oral ulceration or a lichenoid reaction, by contact sensitivity in the intra-oral mucosa, in sensitive patients.
- When applied undiluted to the skin, peppermint oil may cause an icy/hot sensation, allergic reactions, skin rashes, contact dermatitis and eye irritation.
- Pure peppermint oil should never be added to bath water as a severe icy/hot sensation will result. When included in bath blends, peppermint oil should be included as a minor percentage and appropriately diluted in carrier before adding to the bath.
Potential Drug Interactions
- Peppermint leaf essential oil has been shown to slow intestinal transit, which may slow the absorption rate or increase the total absorption of coadministered drugs.
- Peppermint essential oil in large doses internally may inhibit the drug-metabilizing isoenzyme CYP3A4, leading to increased plasma levels of drugs metabolized by that isoenzyme.
- Coadministration of peppermint leaf essential oil (600mg) and felodipine (a calcium antagonist drug used to control hypertension) moderately increased the plasma concentration of felodipine, possibly through inhibition of the drug-metabilizing isoenzyme CYP3A4.
- Peppermint oil, menthol, menthyl acetate, and ascorbyl palmitate were moderately potent reversible inhibitors of in vitro CYP3A4 activity. Grapefruit juice increased the oral bioavailability of felodipine by inhibition of CYP3A4-mediated presystemic drug metabolism. Peppermint oil may also have acted by this mechanism. However, this requires further investigation. Ascorbyl palmitate did not inhibit CYP3A4 activity in vivo.
References:
https://nccih.nih.gov/health/peppermintoil
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2967840
https://onlinelibrary.wiley.com/doi/pdf/10.1002/ffj.3252
