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Allergy and anaesthesia
Understand a reaction during a procedure and prepare for future anaesthesia
In this sheet
Three essential points
A reaction in theatre does not mean allergy to every anaesthetic
An antibiotic, neuromuscular blocking agent (NMBA), antiseptic such as chlorhexidine, latex or other perioperative product may be involved. The exact timeline is essential.
Operating-theatre records are valuable
The anaesthetic record, timed medication chart, incident report and tryptase results may allow the reaction to be reconstructed.
Further anaesthesia is usually still possible
Assessment is not intended to ban every anaesthetic, but to specify what should be avoided, what remains uncertain and which alternatives may be used.
Why is it not necessarily ‘the drug that put me to sleep’?
Around anaesthesia, several products may be given within a few minutes: antibiotics, neuromuscular blocking agents (NMBAs), hypnotics, analgesics, antiseptics, chlorhexidine-containing devices, latex, dyes or other medical products.
Close timing alone is not enough to identify the cause. The clinical history and exact exposure list are essential.
Which documents should be kept?
- Document
- Anaesthetic record
- Why it is useful
- Helps reconstruct the timeline and products given.
- Document
- Medication chart / times
- Why it is useful
- Shows which product preceded the first signs.
- Document
- Incident report
- Why it is useful
- Describes the reaction, its severity and treatment received.
- Document
- Tryptase results
- Why it is useful
- May help document mast-cell activation if samples were taken.
- Document
- Final allergy-clinic letter
- Why it is useful
- Should ideally specify what is confirmed, what remains suspected and what may be used.
| Document | Why it is useful |
|---|---|
| Anaesthetic record | Helps reconstruct the timeline and products given. |
| Medication chart / times | Shows which product preceded the first signs. |
| Incident report | Describes the reaction, its severity and treatment received. |
| Tryptase results | May help document mast-cell activation if samples were taken. |
| Final allergy-clinic letter | Should ideally specify what is confirmed, what remains suspected and what may be used. |
When is the reaction an emergency?
A severe reaction may occur without visible hives
During anaesthesia, skin signs may be absent or difficult to see. A fall in blood pressure, bronchospasm, breathing difficulty or a rapidly progressing presentation may be part of perioperative anaphylaxis.
Emergency treatment takes priority. It must never be delayed to obtain a sample or wait for allergy advice.
Understand and organise assessment
Why is tryptase sometimes measured?
Tryptase sampled during the reaction may support mast-cell activation. It must be interpreted alongside a baseline value measured after the episode has completely resolved and the clinical context.
A tryptase result that does not rise does not formally rule out a perioperative hypersensitivity reaction.
When is allergy assessment performed?
After a perioperative reaction, the allergist selects products for investigation from the actual timeline. French recommendations generally suggest waiting at least four weeks after the reaction has resolved before skin tests, to improve sensitivity.
If another procedure is urgent, the specialist team may sometimes decide on an earlier strategy; some early negative results may then need to be checked again.
Should tests be done ‘just in case’ before every anaesthetic?
No. Without a relevant history or risk factor, routine allergy screening before anaesthesia is not recommended. Tests without an indication may produce difficult-to-interpret results and unnecessarily exclude useful products.
However, a personal history of an unexplained or never-investigated perioperative reaction must be reported before another procedure.
What if assessment finds no responsible product?
A negative assessment does not mean the reaction ‘did not happen’. Some mechanisms are hard to demonstrate, information may be missing and no test is perfect. The aim remains to prepare a safe strategy with the allergist and anaesthetist.
Mastocytosis, MCAS or hereditary alpha-tryptasemia
These situations may justify individual preparation and discussion between the allergist and anaesthetist. There is no single rule that applies to every patient.
Frequently asked questions
- Question
- ‘Egg or soy allergy means propofol is forbidden?’
- Answer
- Not automatically. French recommendations do not justify routinely excluding propofol for this reason alone.
- Question
- ‘Shellfish allergy means iodine allergy?’
- Answer
- No. Fish or shellfish allergy is not an allergy to ‘iodine’. Reactions to contrast media are a separate subject.
- Question
- ‘Chlorhexidine? I do not know this product.’
- Answer
- This antiseptic may be present in products or devices used in healthcare. A confirmed allergy must be clearly reported.
- Question
- ‘Latex allergy?’
- Answer
- If known or strongly suspected, the team can arrange an appropriate environment. A history involving a cross-reactive food alone is not enough to make the diagnosis.
- Question
- ‘Old penicillin allergy?’
- Answer
- An old, poorly documented label may be worth clarifying instead of being copied automatically for life.
| Question | Answer |
|---|---|
| ‘Egg or soy allergy means propofol is forbidden?’ | Not automatically. French recommendations do not justify routinely excluding propofol for this reason alone. |
| ‘Shellfish allergy means iodine allergy?’ | No. Fish or shellfish allergy is not an allergy to ‘iodine’. Reactions to contrast media are a separate subject. |
| ‘Chlorhexidine? I do not know this product.’ | This antiseptic may be present in products or devices used in healthcare. A confirmed allergy must be clearly reported. |
| ‘Latex allergy?’ | If known or strongly suspected, the team can arrange an appropriate environment. A history involving a cross-reactive food alone is not enough to make the diagnosis. |
| ‘Old penicillin allergy?’ | An old, poorly documented label may be worth clarifying instead of being copied automatically for life. |
Specific situations
Chlorhexidine: a sometimes hidden allergen
Chlorhexidine is used as an antiseptic and may also be present in some gels, dressings or medical devices. A confirmed allergy must be stated explicitly before healthcare and procedures.
Latex: important, without shortcuts
Known latex allergy may require specific precautions in theatre. However, sensitisation or a reaction to certain foods associated with latex-fruit syndrome does not automatically mean latex allergy.
Old ‘penicillin allergy’
Antibiotic prophylaxis is often given around surgery. An old beta-lactam allergy label may be inaccurate or poorly documented. Clarifying it may prevent the use of less suitable alternatives.
What should the final allergy-clinic letter specify?
- the reaction that led to assessment;
- products confirmed as responsible or to be avoided;
- products tested and considered usable in the context of assessment;
- remaining uncertainties;
- recommendations for future anaesthesia.
Prepare for your consultation
- What to prepare
- Previous procedure
- Useful information
- Date, hospital, type of operation and description of the reaction.
- What to prepare
- Documents
- Useful information
- Anaesthetic record, medication chart, incident report and tryptase results.
- What to prepare
- Allergy assessment
- Useful information
- Final letter, tests performed, products to avoid and products considered usable.
- What to prepare
- Future procedure
- Useful information
- Planned date, type of procedure and anaesthetic-team contact details if known.
- What to prepare
- Medication list
- Useful information
- Current medicines, particularly cardiovascular treatment, without stopping anything on your own.
| What to prepare | Useful information |
|---|---|
| Previous procedure | Date, hospital, type of operation and description of the reaction. |
| Documents | Anaesthetic record, medication chart, incident report and tryptase results. |
| Allergy assessment | Final letter, tests performed, products to avoid and products considered usable. |
| Future procedure | Planned date, type of procedure and anaesthetic-team contact details if known. |
| Medication list | Current medicines, particularly cardiovascular treatment, without stopping anything on your own. |
Common myths
- Myth
- ‘I reacted in theatre, so I am allergic to anaesthesia.’
- SOS Allergo message
- Not necessarily. Several products are used almost simultaneously.
- Myth
- ‘Anyone with allergies must test every anaesthetic before an operation.’
- SOS Allergo message
- No. Routine screening without a risk factor is not recommended.
- Myth
- ‘Egg allergy means no propofol.’
- SOS Allergo message
- Not automatically.
- Myth
- ‘Shellfish allergy means iodine allergy.’
- SOS Allergo message
- No.
- Myth
- ‘Normal tryptase means no hypersensitivity.’
- SOS Allergo message
- No. The result must be interpreted in the full context.
- Myth
- ‘A negative assessment means I can never have anaesthesia again.’
- SOS Allergo message
- False. The purpose of assessment is precisely to prepare a safe strategy.
| Myth | SOS Allergo message |
|---|---|
| ‘I reacted in theatre, so I am allergic to anaesthesia.’ | Not necessarily. Several products are used almost simultaneously. |
| ‘Anyone with allergies must test every anaesthetic before an operation.’ | No. Routine screening without a risk factor is not recommended. |
| ‘Egg allergy means no propofol.’ | Not automatically. |
| ‘Shellfish allergy means iodine allergy.’ | No. |
| ‘Normal tryptase means no hypersensitivity.’ | No. The result must be interpreted in the full context. |
| ‘A negative assessment means I can never have anaesthesia again.’ | False. The purpose of assessment is precisely to prepare a safe strategy. |
Key points
- A reaction during anaesthesia does not mean allergy to every anaesthetic.
- Keep the operating-theatre records: the product timeline is essential for assessment.
- Routine allergy screening before every anaesthetic is not recommended without an indication.
- Egg or soy allergy does not automatically prohibit propofol; shellfish allergy is not iodine allergy.
- The aim of assessment is to allow future anaesthesia with precise, safe instructions.
You may also want to read
Main references
- SFAR-SFA. Diagnostic et prise en charge des réactions d’hypersensibilité immédiate périopératoires. Recommandations Formalisées d’Experts (RFE). 2025. Dernière version à jour publiée par la SFAR.
- Garvey LH, Ebo DG, Mertes PM, et al. An EAACI position paper on the investigation of perioperative immediate hypersensitivity reactions. Allergy. 2019;74(10):1872-1884. DOI: 10.1111/all.13820. PMID: 30964555.
- Garvey LH, Melchiors BB, Ebo DG, Mertes PM, Krøigaard M. Medical algorithms: Diagnosis and investigation of perioperative immediate hypersensitivity reactions. Allergy. 2020;75(8):2139-2142. DOI: 10.1111/all.14226. PMID: 32053736.
- Mertes PM, Tacquard C. Perioperative anaphylaxis: when the allergological work-up goes negative. Curr Opin Allergy Clin Immunol. 2023;23(4):287-293. DOI: 10.1097/ACI.0000000000000912. PMID: 37357801.
General information: this sheet does not make a diagnosis and does not replace allergy consultation or instructions from the anaesthetic team. In a severe acute reaction, emergency care takes priority.
Scientific review: September 2026 · sosallergo.fr