Anaesthetic
A medicine that removes sensation or produces controlled unconsciousness for a procedure.
What it means
An anaesthetic abolishes sensation. From the Greek an-, without, and aisthesis, sensation.
Three distinct kinds, frequently confused:
- Local — numbs a small area only; the patient is fully awake. Lidocaine injected before stitching or a skin biopsy.
- Regional — numbs a whole region by blocking nerves; the patient is awake or lightly sedated. An epidural or a nerve block.
- General — controlled unconsciousness, with breathing usually supported.
Sedation is not anaesthesia. It reduces awareness and anxiety but does not abolish sensation, and is often combined with a local anaesthetic.
In practice
Written as "under LA" or "under GA" in procedure notes.
Local anaesthetics work poorly in infected or inflamed tissue, which is why an abscess can remain painful to drain despite generous injection.
Why it matters
A reported "allergy" to local anaesthetic is usually a reaction to adrenaline mixed with it, or a faint, rather than true allergy — true local anaesthetic allergy is genuinely rare, and being wrongly labelled leads to unnecessary general anaesthetics.
Anyone who has had an unexpected reaction to an anaesthetic, or has a family history of one, should mention it before any procedure.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026