An unexpected allergic skin reaction to peppermint oil capsules
- Gabrielle Sanders
- Obstetrics and Gynaecology, Colchester Hospital, East Suffolk and North Essex NHS Foundation Trust, Colchester, UK
- Correspondence to Dr Gabrielle Sanders; gabriellesanders01@gmail.com
Abstract
Peppermint oil capsules are prescribed to manage abdominal colic and distension, a common complaint in postcaesarean section patients. Arachis (peanut) oil is contained within one frequently prescribed peppermint formulation: Colpermin. This ingredient is contraindicated in patients with peanut and soya allergy; however, this is not stated in the side effects or contraindications section of the British National Formulary, or present on the medication packaging. A postpartum woman in her early 30s had an unexpected allergic reaction to the capsules, in the form of a generalised body rash, fortunately with no anaphylactic features. The patient reported the same reaction to soya in the past. After review of the patient’s clinical and medication history, Colpermin capsules were thought to be responsible for the patient’s symptoms. This case highlights the necessity for clearer documentation in prescribing formularies and on medication packaging to ensure patient safety.
Background
Peppermint oil capsules are prescribed to manage abdominal colic and distension, particularly common in postcaesarean section patients. They are also available on medical and surgical wards1 in primary care and can be purchased over-the-counter.
There are eight brands of peppermint oil stated in the British National Formulary (BNF). Colpermin is the only preparation, which contains arachis oil (peanut oil).2 In the BNF, the potential for Colpermin to trigger peanut allergy is not stated within the side effects section and there are no highlighted contraindications. The peppermint oil profile in the electronic BNF contains a separate link to medicinal forms. The medicinal forms page contains an excipients section, where it is stated ‘may contain arachis (peanut) oil’, and there is no mention of the potential for cross reactivity to soya.3 The patient information leaflet, found inside of the medication packaging states in small print ‘do not take this medication if you are allergic to peanuts or soya’.4 Many clinical staff and patients are not aware of this risk.
According to the British Society of Allergy and Clinical Immunology (BSACI), nut allergy affects approximately 2% of children and 0.5% of adults in the UK.5 In the UK, it is estimated 220 000 people up to the age of 44 years have had a nut-induced anaphylactic reaction.6 BSACI guidelines on diagnosis and management of peanut and tree nut allergy caution that ‘peanut-allergic individuals may be sensitised to legumes (soya, pea and chickpea)’, hence why soya allergic patients should not be prescribed medications with arachis oil.7 The prevalence of soya allergy is estimated to be less than 1% in both adults and children.8
Case presentation
A patient in her early 30s, day 1 post caesarean section, developed an acute rash on both of her wrists, originating first on her left wrist and subsequently the right wrist. The patient was observed to be scratching at these. The patient denied any airway tightness, shortness of breath, wheeze or palpitations. The patient had experienced the same rash in the past, specifically to soya; this allergy was reported to be ‘very sensitive’ and the rash eruption was known to occur in response to traces of soya in food. The patient denied any drug allergies or previous adverse drug reactions. These details were also documented in the patient’s drug chart.
Medications initiated that day included Colpermin capsules, chlorphenamine and lactulose. Regular morphine was initiated during the previous day which had not caused any adverse reaction. The patient had eaten toast from the hospital canteen and no other meals or snacks to cause such a reaction. Other causes for rash onset were also explored, such as anxiety.
Examination at the time revealed a clear airway with no additional sounds suggestive of airway compromise. The patient’s lung fields were clear on auscultation with no wheeze. On inspection of the patient’s skin a rash was seen on both wrists with visible scratch marks. No other rashes were present elsewhere at the time of initial examination. The patient’s heart rate and blood pressure were stable and her respiratory rate within normal limits.
Differential diagnosis
Differential diagnoses included an adverse drug reaction, potential food contaminant from the canteen or reaction secondary to anxiety.
Skin reactions are a common side effect of morphine. However, the patient was taking this medication regularly for 24 hours prior to rash onset and no problems ensued. Thus, morphine is unlikely to have caused these new skin symptoms.
The newly prescribed medications: chlorphenamine, lactulose and Colpermin capsules were explored. Soya allergy was not documented in the BNF—in neither the side effect nor contraindication section for any of these medications. The active ingredients were then investigated for each. Avoidance in soya allergy was documented at the bottom of page 1 in the patient information leaflet of the brand of peppermint oil capsules prescribed. There was no such association on investigation of the excipients for chlorphenamine or lactulose.
Treatment
The Colpermin capsules which were prescribed on an ‘as required’ basis were discontinued and the patient was given 4 mg chlorphenamine immediately. A note was then made on the patient’s drug chart to include peppermint oil capsules and soya as allergies. Hospital catering staff were informed to keep this patient’s food separate to avoid potential contact with soya. The incident was explained to the patient, and she was educated on the potential for food allergies to trigger an allergic reaction to certain medications. The patient was advised to inform staff immediately in the event of new-onset chest tightness, wheeze or airway swelling as this could be anaphylaxis, which is life-threatening and necessitates urgent treatment. All staff members in the department were informed of the incident and it was formally reported as a datix. The National Health Service (NHS) use the datix risk management system to collect and manage data on anonymised adverse events in order to recognise learning points and improve the delivery of healthcare for patients and staff.
Outcome and follow-up
During the subsequent morning’s ward round, the patient reported in retrospect that the rash had worsened during the evening, spreading to other areas of her body; the chest, abdomen and hands, but had improved without intervention. The rash did not spread to her face, cause new wheeze or airway swelling. No further rash eruptions occurred following discontinuation of the peppermint oil capsules. The patient’s clinical and vital signs remained stable throughout, demonstrating no concerning features of possible airway compromise or haemodynamic instability. The incident initiated a quality improvement project at the hospital to spread awareness of peanut and soya allergy contraindications to peppermint oil capsules and the importance of screening for these prior to prescription.
Discussion
It was not widely known among prescribers in the team that peanut or soya allergy is a contraindication to peppermint oil capsules. This is not an isolated case; it has been documented in an array of contexts that prescribers were not aware arachis oil was present in the medicines they prescribed, or failed to ask patients if they were allergic to peanuts or soya beforehand.9–11 Moreover, the dispenser and patient may not understand the pharmaceutical jargon if they are notified a medication contains ‘arachis oil’ .10
The Committee on Safety of Medicines, an independent committee that advise the UK Licensing Authority on the efficacy and safety of medicines, reviewed allergic reactions associated with medicinal products containing peanut oil. They advised the likelihood of allergic reaction to peanut oil used in pharmaceuticals is low since it is refined, which involves removing the peanut protein during manufacture.12 However, it has been demonstrated that very small amounts of allergenic peanut protein may remain in the refined oil.13
An in-depth qualitative study into the causes of prescribing errors by foundation trainees found the main factors contributing to knowledge-based errors were high workload, busyness and lack of senior support and communication. The latter included themes such as lack of awareness of pharmacy services and the BNF being unclear or insufficient.14 These factors highlight the need for signposted information in the BNF to avoid prescribing errors that may occur due to a lack of awareness and time constraints among medical staff.
Research has highlighted the lack of engagement the general population have with patient information leaflets. A self-report study of 800 respondents found 1 in 4 participants read the patient information leaflet in full when purchasing a medicine they have never used before, and little attention is paid to the contra-indications and warning section. Age and gender are also factors—females and those over 65 years in age were found more likely to read the leaflets.15 Another self-report study of 307 patients in New York found 49.2% always read the patient information leaflets, 21.2% often and 29.7% seldom or never, for new medications.16 This highlights the necessity for such information to be clearly displayed on multiple resources, including prescribing formularies and on medication packaging. This creates a comprehensive approach, whereby all stakeholders including prescribers, pharmacists and patients are adequately informed, minimising the reliance on one single factor to protect patient safety.
The Swiss cheese model of errors describes how in a complex system, hazards resulting from human error are prevented with a series of layers. Each layer has random unforeseen holes and when by chance these holes align, the hazard reaches the patient and causes harm.17 Relying on human memory alone to screen for such allergies some of the time, or most of the time, allows patient safety to slip through the net. Peppermint water is an alternative peppermint formulation which does not contain arachis oil. It is a slightly more expensive preparation since greater doses of the liquid are required to achieve the desired effects; one dose of the liquid costs £1–£4 compared with 13–28 p for one dose of the capsules. As this preparation does not contain traces of arachis oil, the risk to patients with soya and peanut allergy will be removed. The disadvantage of additional cost vs benefits to patient safety are debateable with this solution.
Other food allergies relevant to medicine include the association between exotic fruit and/or nut allergies, and latex hypersensitivity 18 fish allergy and protamine use,19 and the presence of soybean oil in isotretinoin, alitretinoin and oral retinoids.20 Although the European Medicines Agency advise medicinal products containing soya should be avoided in individuals hypersensitive to soya or peanuts,21 this warning may not be stated by all products. There may also be inconsistency in identifying soya oil as an excipient in the Summary of Product Characteristics, with other terms such as ‘edible fats’ or ‘vegetable oils’ sometimes used.7 Inconsistencies in the information available to the general public will also create confusion. The NHS medicine guide for peppermint oil, for example, highlights the potential for adverse events in patients with peanut allergy but does not mention soya allergies.22
In the food industry, there is a direction that any presence of ‘soybeans and products thereof’ (including soya lecithin) must be declared by law, as an allergen on the packaging. This is not the case for medicine, whereby there is no legal requirement to clearly state allergies on medication packaging. However, the Medicines and Healthcare products Regulatory Agency do expect companies to include a ‘warnings’ section stated ‘on the label and/or in the leaflet’.23 As outlined above, the patient information leaflet alone is insufficient warning of potential allergy as this information is so frequently overlooked. Packaging is important as this is seen by the prescriber, administrator and the consumer, therefore, creating more barriers to potential adverse events.
Although this case describes an adverse drug reaction in obstetrics and gynaecology, this is not exclusively a women’s health issue; peppermint oil capsules are distributed in general practice, gastroenterology, care of the elderly, postoperatively and even purchased over-the-counter. There are many medications which contain arachis oil,9 24 therefore, it is important awareness is raised of the associated contraindications.
Learning points
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Preadmission checks should include questioning about food allergies and these should be documented clearly alongside drug allergies and adverse reactions in a patient’s medical notes. Prescribers and hospital pharmacists have a responsibility to ensure prescribing is congruent with these.
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Prescribers should always review the excipients list and consult multiple pharmaceutical resources if there is doubt, including the British National Formulary, electronic medicines compendium, hospital pharmacy or intranet, prior to medication prescription to prevent harm to the patient.
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Patients, prescribers and medicine administrators (including nurses, midwives and pharmacists) should all be aware of the potential for food allergies to cross react with medications.
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Medication manufacturers should clearly document allergy warnings to the product ingredients and excipients in prescribing formularies and on packaging (clear eye-catching symbols may suffice on external packaging for the purposes of space and audience attention).
Ethics statements
Patient consent for publication
Acknowledgments
Thank you to the patient who consented to the description of her experience in an anonymous account. Thank you to the midwifery team at the Hospital who escalated the patients adverse reaction promptly and ensured the patient was monitored appropriately in the hours after the adverse reaction. Thank you to Miss Osbourne, consultant obstetrician and gynaecologist who was my clinical supervisor whilst on my O&G rotation, encouraged me to reflect on the experience, including how food allergies appear in other aspects of medicine and advised me to escalate the incident to the MHRA and medicines information at my Hospital. Thank you to the pharmacists working in the obstetric and gynaecology department, particularly David Cushing, who designed warning labels for the peppermint capsule packaging to highlight peanut and soya allergy contraindications. Thank you to the doctors working in the obstetric and gynaecology department between March and April 2022 who were very receptive to the incident and took part in a quality improvement initiative to improve screening for allergies prior to prescribing peppermint capsules and medications in general.
Footnotes
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Contributors GS confirms that GS is sole author of this case report and received no assistance with writing. GS was the junior doctor in this case which responded to the patients rash and identified the underlying cause.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
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Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2023. No commercial re-use. See rights and permissions. Published by BMJ.
References
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