Topical benzocaine is a local anesthetic that blocks nerve signals, providing short-term relief for minor irritations. Available in many forms, including gels, sprays, liquids, and ointments, it is a common over-the-counter ingredient for external use on skin or mucous membranes. It is generally intended for temporary use.
Typical Duration of Relief
The numbing effect of topical benzocaine begins quickly, often within seconds to a minute. Pain relief typically lasts briefly, generally 5 to 15 minutes. Some stronger formulations might provide a noticeable effect for up to an hour, though this extended duration is less common and often at a diminished intensity.
When applied orally for issues like toothaches or canker sores, saliva can quickly dilute and wash away the product, often limiting the numbing effect to 5 to 15 minutes. Sprays used for sore throats might numb the area for approximately 15 minutes. When applied to the skin for minor irritations such as insect bites or small cuts, the effect may last slightly longer than on mucous membranes, generally providing relief for 5 to 10 minutes.
Factors Influencing How Long It Lasts
The concentration of benzocaine in the product plays a role; higher concentrations generally lead to a more pronounced numbing effect and potentially a slightly longer duration. Products can range from 5% to 20% benzocaine, with 20% being a common concentration in dental applications.
The specific formulation of the product also affects its performance. Gels, sprays, liquids, lozenges, and ointments differ in how well they adhere to the application site and how deeply they penetrate the tissue. For example, gels might seep into tissues more gradually, potentially extending the effect, while liquids or sprays might have a quicker onset but wear off faster.
The application site itself is a significant factor. Mucous membranes, such as those inside the mouth or throat, tend to absorb benzocaine faster than intact skin due to their thinner and more permeable nature. This faster absorption can lead to a quicker onset of action but often a shorter overall duration of effect compared to application on skin.
Individual biological differences, including metabolism and sensitivity, also contribute to how long the medication lasts. Benzocaine is metabolized in the body, primarily by an enzyme called pseudocholinesterase. Variations in this enzyme’s activity can affect how quickly the body processes and eliminates the drug, thus influencing the duration of its effect.
The severity of the pain or condition being treated can also influence the perceived duration of relief; more intense pain might seem to break through the numbing effect sooner. Additionally, the method of application, including using the correct amount and ensuring proper coverage, is important for achieving the expected duration of relief.
Safe Application and Important Considerations
Using topical benzocaine safely requires adherence to product instructions and awareness of potential risks. Apply only the smallest amount needed to relieve pain, avoiding large areas of the body, broken or inflamed skin, or severe burns. Most products recommend applying it no more than three or four times a day. Prolonged use, generally exceeding seven days, is not advised without consulting a healthcare provider.
Mild side effects include temporary stinging, burning, or redness at the application site. A rare but serious side effect called methemoglobinemia can occur, where the blood’s ability to carry oxygen is reduced. This condition is particularly concerning in infants and young children under two years of age, and the FDA advises against using oral benzocaine products for teething pain in this age group.
Symptoms of methemoglobinemia may appear within minutes to two hours after use and can include pale, gray, or blue-colored skin, shortness of breath, headache, fatigue, confusion, or a fast heart rate. If these symptoms occur, immediate medical attention is necessary.
Allergic reactions, though rare, are also possible, manifesting as hives, difficulty breathing, or swelling of the face, lips, tongue, or throat. It is important to avoid getting benzocaine into the eyes; if this occurs, rinse thoroughly with water.
Seek medical advice if pain persists, worsens, or if any severe or unusual reactions develop. Proper storage, typically at room temperature in a cool, dry place and out of reach of children, helps maintain the product’s effectiveness and safety.