A patient reports being allergic to local anaesthetic. It is recorded in the notes, it follows them from clinic to clinic, and it limits their care for years.
In most cases it is not an allergy at all.
Ask what happened, and where
Gisele J. Girault, MD does not accept the label at face value. When a patient reports a reaction to local anaesthetic, “I always ask them what happened.”
The description that comes back is usually a version of the same thing: a racing heart, flushing, feeling light-headed, sometimes nearly fainting. It came on within moments of the injection and settled within minutes.
And the setting is almost always the same: the dentist's chair.
What that reaction actually was
Dentists commonly use local anaesthetic combined with epinephrine, which prolongs the block and reduces bleeding.
If some of that mixture enters a blood vessel — not difficult in a well-vascularised mouth — the patient receives a small intravascular dose of epinephrine. Tachycardia, flushing and light-headedness follow, sometimes with a vasovagal episode afterwards as the patient responds to the alarming sensation.
Girault's conclusion is direct: “That's not an allergy to local anaesthetics.”
It is a predictable pharmacological response to epinephrine, in a patient who was never allergic to the anaesthetic at all.
How the two actually differ
| Epinephrine response | True allergic reaction | |
|---|---|---|
| Onset | Within seconds, during injection | Usually minutes afterwards |
| Heart | Racing, forceful, palpitations | Fast but with falling blood pressure |
| Skin | Flushing, pallor | Urticaria, itching, swelling |
| Breathing | Unaffected | Wheeze, throat tightness, stridor |
| Course | Settles within minutes | Progresses without treatment |
| Setting | Typically dental | Any |
Itching, hives, swelling or any breathing difficulty is a different story and should be taken seriously. Palpitations and flushing that resolved on their own in a dental chair is a different story again.
Why the distinction is worth the two minutes
A patient carrying an incorrect local anaesthetic allergy label loses access to a great deal:
- Joint and trigger point injections that would otherwise be straightforward
- Diagnostic blocks, where the anaesthetic is the diagnostic test
- Comfortable dental treatment, indefinitely
- Minor procedures that would otherwise need no more than local infiltration
And the label is self-perpetuating. Once recorded, each subsequent clinician reasonably declines to be the one who challenges it.
True allergy is genuinely rare
Real allergy to amide local anaesthetics — lidocaine, bupivacaine, ropivacaine — is uncommon. Where reactions have been documented historically, preservatives and ester-class agents accounted for a substantial share.
That does not mean it never occurs, and a patient describing urticaria, facial or airway swelling, or wheeze deserves formal allergy assessment rather than reassurance. The point is not to dismiss the report but to establish what it actually describes.
The related rule: keep epinephrine out of the building
The same drug creates a second, more serious problem, and Girault's handling of it is worth copying.
Epinephrine causes vasoconstriction. Injected into or near an end-artery supplying a digit or other appendage, the tissue supplied can become ischaemic and necrose.
Her mitigation is not labelling or care. It is absence: she does not keep local anaesthetic with epinephrine in the office at all, because “I don't want there to be an accidental mix up… there could be a mixup.”
A vial that is not in the room cannot be drawn up in error at the end of a long clinic list. Systems that remove the possibility outperform systems that rely on vigilance.
What to do with the label
- Ask what happened — symptoms, timing, and how it resolved.
- Ask where — a dental setting raises the epinephrine explanation immediately.
- Ask which drug, if they know. Many will not, and that is informative in itself.
- Separate the two pictures. Palpitations and flushing that settled is not urticaria and wheeze.
- Refer for allergy testing where the description genuinely suggests hypersensitivity.
- Correct the record where it does not. Leaving an incorrect label in place costs the patient for years.
If you are the patient
If you have been told you are allergic to local anaesthetic, it is worth establishing whether you are.
Try to recall what you felt, how quickly it started, how long it lasted, and where you were. A racing heart and flushing at the dentist that settled in a few minutes has a well-recognised explanation that is not allergy — and confirming that could restore a range of treatment to you.
Learn blocks with your hands, not from a page
Empire’s Pain Management Training (THE Pain Show) is accredited for 25.25 AMA PRA Category 1 Credits™, jointly provided by AKH, Inc, and Empire Medical Training. For narrower peripheral work, Joint, Extremity and Non-Spinal Injection Training carries 6.75 credits for the complete in-person hybrid program, and Advanced Musculoskeletal Ultrasound Guided Injections builds the guidance skills above.
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