What are Local Anaesthetic Creams?
Local anaesthetic creams, also known as numbing creams, are topical medications applied to the skin to cause a temporary loss of sensation, including pain [1.8.5]. They work by blocking nerve signals in the skin from reaching the brain [1.2.3]. These creams are widely used to prevent pain from minor medical and cosmetic procedures, such as injections, blood draws, tattooing, and laser treatments [1.8.1, 1.8.5]. The active ingredients are typically 'caine' anaesthetics, with lidocaine being one of the most common [1.5.6]. Others include benzocaine, tetracaine, and prilocaine. Some formulations, like EMLA (Eutectic Mixture of Local Anesthetics), combine agents like lidocaine and prilocaine for enhanced effect [1.6.3].
The Onset of Action: How Long Until It's Numb?
The primary question for users is, how long does local anaesthetic cream take to work? The general consensus is that most creams begin to produce a numbing effect within 30 to 60 minutes after application [1.2.3]. However, this is a general guideline, and the exact timing can vary significantly.
For instance, some fast-acting 5% lidocaine creams claim to start working in just 3 to 5 minutes, reaching their peak effect in 20-25 minutes [1.3.6]. Formulations like EMLA cream are recommended to be applied at least 60 minutes before a procedure on intact skin [1.6.3]. For deeper anaesthesia required for more significant procedures, an application time of up to 2 hours might be necessary [1.3.1]. On mucous membranes, the onset is much faster, often within 5 to 10 minutes [1.6.3].
Factors Influencing Onset Time
Several factors can influence how quickly and effectively a numbing cream works [1.4.1]:
- Active Ingredients & Concentration: Creams with higher concentrations of active ingredients or specific formulations like liposomal lidocaine may have a faster onset [1.4.1, 1.3.2].
- Application Area: The thickness of the skin plays a crucial role. Creams work faster on areas with thin skin (like the face) and mucous membranes compared to areas with thick skin (like the soles of the feet) [1.4.1].
- Application Method: Applying a thick layer of cream is essential; do not rub it in [1.5.2].
- Occlusion: Covering the applied cream with an occlusive (airtight and watertight) dressing, such as plastic wrap, significantly enhances absorption and speeds up the numbing process [1.5.1, 1.4.1].
- Skin Condition: The cream should only be applied to intact, unbroken skin. Application on damaged or inflamed skin can lead to faster, excessive absorption and increase the risk of side effects [1.5.5].
- Temperature: Heat can speed up absorption, but it can also increase the risk of systemic side effects. It is generally advised to avoid applying heat sources over the cream [1.7.1].
Comparison of Common Anaesthetic Creams
Different products have different properties. Here is a comparison of some common types:
| Anaesthetic Agent(s) | Common Brand Name(s) | Typical Onset Time (on intact skin) | Peak Effect | Duration After Removal |
|---|---|---|---|---|
| Lidocaine | LMX 4, Zensa | 25-60 minutes [1.2.1, 1.3.5] | 35-40 minutes [1.2.4] | 1-2 hours [1.6.2] |
| Lidocaine & Prilocaine | EMLA | 60 minutes [1.6.3] | 2-3 hours [1.6.3] | 1-2 hours [1.6.3] |
| Lidocaine & Tetracaine | Pliaglis, Synera | 20-30 minutes [1.3.1] | Varies by procedure | Varies |
| Benzocaine | Orajel (and others) | Fast onset, often for mucous membranes [1.8.5] | Quick | Shorter duration |
How to Apply Local Anaesthetic Cream Correctly
Proper application is critical for both efficacy and safety. Follow these steps [1.5.1, 1.5.5]:
- Wash and Dry: Clean the target area with mild soap and water, then pat it completely dry.
- Apply a Thick Layer: Squeeze the cream directly onto the skin. Apply a thick layer; do not rub it in. The amount will depend on the area size, but a dime-to-quarter-sized amount is often sufficient for small sites [1.5.4].
- Cover the Area: Place an occlusive dressing over the cream to keep it from drying out and to enhance absorption. Plastic wrap can also be used [1.5.2, 1.6.1].
- Wait: Leave the cream and dressing in place for the recommended amount of time, typically 30-60 minutes, or as directed by a healthcare professional [1.2.2].
- Remove: Just before the procedure, remove the dressing and wipe away all the excess cream.
- Wash Hands: Wash your hands thoroughly after application to avoid accidentally numbing other areas [1.5.1].
Potential Side Effects
While generally safe when used correctly, local anaesthetic creams can have side effects. Common, mild effects at the application site include redness, swelling, skin discoloration (paleness), or a burning sensation [1.3.1, 1.7.4].
Serious side effects are rare but can occur, especially if too much cream is used, it's applied to a large area, or used on broken skin [1.5.3, 1.8.5]. These can include systemic effects like dizziness, blurred vision, irregular heartbeat, and in very rare cases, seizures or cardiac arrest [1.7.1, 1.7.5]. A rare but serious blood disorder called methemoglobinemia can also occur, with symptoms like pale or bluish skin, headache, and shortness of breath [1.7.2, 1.7.4].
Conclusion
Local anaesthetic creams are effective tools for managing pain during minor procedures. For most creams, the numbing process takes about 30 to 60 minutes [1.2.3]. Achieving the best results depends on choosing the right product and, most importantly, following the application instructions carefully. Always apply a thick layer to clean, intact skin and cover it with a dressing for the recommended duration. If you have any health conditions or are unsure about usage, consulting with a doctor or pharmacist is the safest course of action.
For more detailed medical information, you can visit the NHS page on lidocaine skin cream.
