What side effects can lidocaine cause?
Lidocaine can cause side effects depending on how it’s used (skin cream/patch, mouth rinse/spray, injection, or topical anesthetic product). Common side effects are usually mild and local, but serious effects can occur if too much is absorbed or if it’s injected incorrectly.
Common, usually mild reactions (topical use)
Topical lidocaine can irritate tissue where it’s applied, with effects such as:
- Skin irritation, redness, or burning at the application site
- Itching
- Numbness/tingling where it’s applied (expected, but can be uncomfortable)
Serious side effects (more likely with high dose, broken skin, or accidental ingestion)
Serious side effects are more concerning and can include signs of lidocaine toxicity (systemic absorption), such as:
- Dizziness, drowsiness
- Nausea or vomiting
- Tremor, confusion, or feeling “out of it”
- Ringing in the ears
- Blurred vision
- Seizures
- Slow or irregular breathing
- Abnormal heart rhythm, low blood pressure, or fainting
Because these can be life-threatening, they warrant urgent medical attention.
When should you get emergency help?
Get emergency care or call local emergency services if lidocaine causes any of the following:
- Trouble breathing, wheezing, or severe shortness of breath
- Swelling of the face, lips, tongue, or throat
- Widespread rash or hives (possible allergic reaction)
- Fainting, severe dizziness, confusion, or seizure
- Chest pain, severe palpitations, or signs of a dangerous heart rhythm
If the lidocaine product was taken by mouth by accident (especially by a child) or used in a way that could lead to large absorption, seek help immediately.
What allergic reactions might look like?
Allergic-type reactions can happen with lidocaine products. Watch for:
- Hives or itchy rash
- Swelling (especially face, lips, or throat)
- Breathing difficulty
These can occur even if you have used lidocaine before, though prior tolerance lowers risk.
How can lidocaine cause toxicity?
Toxicity is more likely when the body absorbs too much lidocaine, which can happen if:
- Large amounts are applied to a wide area
- Lidocaine is applied to broken skin, ulcers, or after shaving/irritation
- It’s used too frequently or left on longer than directed
- It’s used with heat sources (some topical directions warn against this)
- It’s used in children in higher-than-recommended amounts
- It’s injected incorrectly or in excessive dose
With toxicity, symptoms can start with neurologic signs (like dizziness, ringing in ears, tremor) and progress to seizures and heart/breathing problems.
Do side effects differ for creams/patches vs mouth sprays vs injections?
Yes. Side effects depend on the route:
- Skin products (cream/gel/patch): mostly local irritation plus numbness; toxicity is more likely with overuse or broken skin.
- Mouth products (spray/rinse/gel): numb mouth or throat can increase choking risk if sensation is reduced; toxicity can occur if swallowed in large amounts.
- Injections: systemic side effects can occur more readily, and the dose is controlled by clinicians; severe reactions still require urgent care.
What should you do if side effects happen?
- Mild local irritation: stop using the product and call a clinician if symptoms persist or worsen.
- Expected numbness: avoid eating or chewing until numbness fades (especially for mouth products) to prevent biting injury.
- Any signs of allergy, fainting, seizure, severe dizziness, or breathing problems: seek emergency care immediately.
If you tell me the exact lidocaine product (cream/patch/gel/spray/injection) and the dose and where it was applied, I can help narrow down which side effects are most likely and which are red flags.