Many people use numbing creams, also known as topical anesthetics, to reduce pain before minor procedures like waxing, tattooing, or injections. When these products fail to provide relief, it can be frustrating. The effectiveness of numbing cream depends on how the product is used, the physical properties of your skin, and the strength of the anesthetic itself.
How Topical Anesthetics Work
Topical anesthetics temporarily interfere with the transmission of pain signals from the application site to the brain. Active ingredients, such as lidocaine or benzocaine, block the voltage-gated sodium channels located within nerve endings in the skin. These channels control the flow of sodium ions, which is necessary to generate the electrical impulse that signals pain.
By blocking these sodium channels, the anesthetic stabilizes the nerve membrane, preventing depolarization. This stops the nerve impulse from being generated or propagated along the nerve fibers, resulting in a localized and temporary loss of sensation. Since the cream is applied to the skin’s surface, the numbing effect is superficial and targets the nerves closest to the surface.
Application Errors That Reduce Effectiveness
One of the most common reasons numbing cream fails is an error in application technique, which prevents the anesthetic from penetrating the skin barrier effectively. The skin’s outermost layer, the stratum corneum, is a highly effective barrier that resists the absorption of medications.
To overcome this defense, a thick layer of cream must be applied to create a high concentration gradient. Apply a dense, visible layer that is not rubbed completely into the skin, often requiring 1 to 2 grams of cream for every 10 square centimeters of skin. The area must then be covered with an occlusive dressing, such as clear plastic wrap, which traps moisture and heat. This occlusion hydrates the stratum corneum, making it more permeable to the anesthetic molecules.
The time the cream remains on the skin is also a factor for the depth of the numbing effect. Most formulations require at least 60 minutes to achieve effective numbing of superficial nerve endings. To reach a greater depth, such as the 3 to 5 millimeters needed for some procedures, the cream may need to be left on for up to two hours. Removing the cream or the occlusive dressing too early significantly limits absorption and reduces the depth of anesthesia.
Physiological and Product Limitations
Even with perfect application, numbing cream may fail due to factors intrinsic to the body or the product itself. Skin thickness and density vary across the body; areas like the palms, soles, or deeply scarred tissue have a thicker stratum corneum that limits anesthetic penetration. If the procedure penetrates deeper than a few millimeters, a topical cream may be unable to reach the target nerve endings in sufficient concentration.
Individual variability also plays a role in how the body responds to and metabolizes local anesthetics. Some people naturally have sodium channels that are less responsive to the anesthetic molecules. Genetic variations, such as those linked to red hair, have been anecdotally associated with requiring higher doses or different types of anesthesia.
The product’s integrity and concentration are also limitations. Over-the-counter creams are legally restricted to lower concentrations, typically 4% lidocaine or less, which may not be strong enough for certain procedures. Using an expired or improperly stored product can degrade the active ingredients, rendering the cream ineffective regardless of proper application.
What to Do When Creams Fail
If optimized application techniques still result in ineffective numbing, explore professional-grade and prescription alternatives. Your healthcare provider can prescribe higher-concentration topical anesthetics, such as those containing 5% lidocaine or a eutectic mixture of local anesthetics (EMLA). These stronger products are more potent than over-the-counter options and often contain specialized vehicles designed to enhance skin penetration.
When topical medication is unsuccessful, consider non-pharmacological pain management strategies. Applying a cold pack immediately before the procedure can temporarily numb the skin by slowing nerve conduction. Another technique involves using a device that applies high-frequency vibration near the injection site, which can distract nerve signals and reduce pain perception.
You should always consult a healthcare professional to discuss your resistance to topical anesthetics before a procedure. This helps rule out underlying skin conditions or systemic factors that might interfere with absorption or metabolism. A provider can offer injected local anesthesia, which bypasses the skin barrier entirely, or suggest oral pain relievers, such as nonsteroidal anti-inflammatory drugs (NSAIDs), to be taken before the procedure to reduce inflammation and sensitivity.