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Benzocaine Side Effects: What to Expect

Last reviewed: December 2025

Overview

Benzocaine is generally safe when used as directed, with most side effects being mild and temporary. However, there is one rare but serious risk—methemoglobinemia—that has prompted FDA warnings, particularly for use in children under 2 years old. Understanding both common and serious side effects helps ensure safe use.

Common Side Effects

Mild and expected effects:

  • Temporary numbness of surrounding tissue
  • Mild stinging or burning on application
  • Taste changes or unpleasant taste
  • Minor local irritation
  • “Thick” sensation in mouth

These typically:

  • Occur briefly during or after application
  • Resolve within minutes to hours
  • Don’t require stopping the product
  • Are signs the medication is working

Local Reactions

At the application site:

  • Burning or stinging (usually brief)
  • Redness or irritation
  • Mild swelling
  • Tingling sensation

Managing local reactions:

  • Usually resolve on own
  • Try smaller amount next time
  • Consider lower concentration
  • Discontinue if persistent

Serious Side Effect: Methemoglobinemia

What it is: Methemoglobinemia is a condition where the blood cannot carry oxygen effectively. Benzocaine can cause this rare but potentially life-threatening condition.

How it happens:

  • Benzocaine converts hemoglobin to methemoglobin
  • Methemoglobin cannot carry oxygen to tissues
  • Body’s tissues become oxygen-deprived
  • Can occur even with normal use

Risk factors:

  • Age under 2 years (highest risk)
  • Using more than directed
  • Applying to open wounds or broken skin
  • Repeated or prolonged use
  • Certain genetic conditions (G6PD deficiency)
  • Heart or lung problems
  • Smoking

Warning signs (seek emergency help):

  • Pale, gray, or blue-colored skin, lips, or nail beds
  • Shortness of breath
  • Fatigue or weakness
  • Rapid heartbeat
  • Headache
  • Lightheadedness or dizziness
  • Confusion

FDA Warnings

FDA safety communication:

  • Warns against use in children under 2
  • Benzocaine teething products not recommended for infants
  • Products should not be used more than directed
  • Labels must include methemoglobinemia warning

What this means for you:

  • Do not use on children under 2 years old
  • Follow dosing instructions carefully
  • Don’t use more often or longer than directed
  • Be aware of warning signs

Allergic Reactions

Signs of allergic reaction:

  • Rash or hives
  • Swelling of face, lips, tongue
  • Severe itching
  • Difficulty breathing (seek emergency help)

PABA allergy connection:

  • Benzocaine is related to PABA
  • People allergic to PABA may react to benzocaine
  • Also related to other “-caine” anesthetics
  • Inform healthcare providers of allergies

If allergic reaction occurs:

  • Stop using immediately
  • Seek medical help
  • Avoid benzocaine products in future
  • Consider alternative treatments

Effects from Swallowing

If accidentally swallowed:

  • May cause numbness of throat
  • Can affect swallowing temporarily
  • Large amounts may cause systemic effects
  • Contact poison control if significant amount

Preventing swallowing:

  • Use small amounts
  • Apply carefully to targeted area
  • Don’t eat or drink immediately after
  • Supervise children’s use

Who Is at Higher Risk

Higher risk for side effects:

  • Infants and young children (especially under 2)
  • Elderly with respiratory or heart conditions
  • People with G6PD deficiency
  • Those with anemia or breathing problems
  • Smokers (affects oxygen-carrying capacity)
  • People using repeatedly or excessively

Interactions and Increased Risk

May increase risk of methemoglobinemia:

  • Sulfonamide antibiotics
  • Nitrates or nitrites
  • Dapsone
  • Certain antimalarials
  • Other local anesthetics

Inform your doctor if taking:

  • Medications for heart conditions
  • Antibiotics
  • Any medications affecting blood

Comparison to Other Oral Anesthetics

AspectBenzocaineLidocainePhenol
Methemoglobinemia riskYesLowerNo
Allergic potentialModerateLowerLow
Use in children under 2NOWith cautionWith caution
EffectivenessGoodGoodMilder

Minimizing Side Effects

To reduce risks:

  • Use smallest effective amount
  • Don’t exceed recommended frequency
  • Avoid use in children under 2
  • Don’t apply to open wounds
  • Don’t use longer than necessary
  • Watch for warning signs

Signs you should stop using:

  • Persistent irritation
  • Signs of allergic reaction
  • Symptoms of methemoglobinemia
  • Skin discoloration
  • Worsening symptoms

What to Do If Problems Occur

For mild side effects:

  • Reduce amount or frequency
  • Rinse mouth with water
  • Consider lower concentration product
  • Switch to alternative if needed

For serious side effects:

  • Stop using immediately
  • Seek emergency medical care
  • Call 911 for breathing difficulty or blue skin
  • Contact poison control if needed (1-800-222-1222)

Special Populations

Pregnancy:

  • Limited data available
  • Use only if clearly needed
  • Consult healthcare provider
  • Consider alternatives

Breastfeeding:

  • Topical use likely safe
  • Minimal systemic absorption
  • Use smallest effective amount
  • Consult healthcare provider if concerned

Children:

  • NEVER use in children under 2
  • Use child-formulated products for ages 2+
  • Adult supervision required
  • Watch for signs of problems

Sources

  • FDA Drug Safety Communications
  • Product safety labeling
  • Clinical toxicology data
  • Pharmacovigilance reports
Last reviewed: December 2025