The word "topical" refers to a substance that is designed to be placed on the skin or mucous membranes, and anesthetic substances are those which numb sensation, typically during for medical reasons. Various medical procedures or conditions produce pain sensations on the skin, ranging from injections to cosmetic laser techniques. Injections of an anesthetic substance can numb pain in the skin, but a topical anesthetic ointment can also be suitable, and may have the advantage of being easier to use. Unlike a general anesthetic, which puts the whole body to sleep, a topical anesthetic ointment is only used on one small area of the skin at a time.
Ointments are different from other types of external preparations like gels in that they typically have a thick, almost solid texture. A topical anesthetic ointment is always spreadable, and contains the active numbing molecule mixed up with other ingredients that help the consistency or preservation of the product. Examples of active anesthetics that can be present in a topical anesthetic ointment include lidocaine, benzocaine or tetracaine.
Many numbing agents found in topical ointments do not work well on unbroken skin, but for procedures like laser resurfacing of facial skin, the anesthetic effect may be sufficient. Most often, though, a topical anesthetic is used on skin that has been broken or lacerated, to reduce the pain of the injury or the pain of the suturing procedure to fix the damage, and also to save the skin from further pain from injections. After application, the numbing effect takes hold over a few minutes. Burns and skin irritations like allergic dermatitis can also be soothed with anesthetic ointments, and mucous membranes like the oral cavity can also be numbed.
Some side effects can occur with the use of a topical anesthetic ointment. These include a burning sensation when the ointment is applied, a change in skin color at the affected location, and localized swelling. One significant danger of a topical ointment is that the dosage of the drug is not as accurately controlled as in an injection or a tablet. For this reason, only a small amount of skin can be covered with anesthetic ointments, in case too high a dose is absorbed through the skin. Overdoses of the anesthetics can potentially result in heart problems, seizures and even death, especially if the ointment is covered with a dressing that speeds up absorption.