An oral anesthetic is a medication that temporarily numbs tissue inside your mouth or throat to relieve pain or prepare you for a dental procedure. These products range from over-the-counter gels you dab on a canker sore to injectable solutions your dentist uses before a filling. The active ingredients and delivery methods vary, but they all work by blocking nerve signals in the targeted area so you don’t feel pain.
How Oral Anesthetics Work
Every nerve in your mouth transmits pain signals through tiny channels in the nerve cell membrane that open and close to let charged particles (sodium ions) flow through. Oral anesthetics slip into these channels and physically block that flow. When sodium can’t move through the channel, the nerve can’t fire a pain signal to your brain. The area goes numb.
This blocking effect is temporary. As your body metabolizes the anesthetic and clears it from the tissue, the channels reopen and normal sensation returns. Topical products applied to the surface wear off faster because they only penetrate the outermost nerve endings. Injectable anesthetics reach deeper nerves and last longer, which is why your lip or jaw can stay numb for hours after a dental visit.
Topical vs. Injectable Types
Oral anesthetics fall into two broad categories based on how they’re delivered.
Topical anesthetics come as gels, ointments, sprays, liquids, and pastes that you apply directly to the surface of your gums, inner cheeks, or throat. They numb only the top layer of tissue. Common brand names include Orajel, Anbesol, and Chloraseptic. Dentists also use topical gels to numb your gums before giving an injection, so the needle itself hurts less. Throat sprays serve a different purpose: they suppress your gag reflex before procedures like an endoscopy.
Injectable anesthetics are administered by a dentist or oral surgeon using a small needle. The solution is deposited near specific nerves deeper in the tissue, producing a more complete and longer-lasting numbness over a wider area. This is what you receive before fillings, root canals, extractions, and other procedures where surface numbing alone wouldn’t be enough.
Common Active Ingredients
Lidocaine is the most widely used local anesthetic in dentistry today. It’s found in both injectable and topical forms, including a viscous (thick liquid) version that can be swished in the mouth to coat sore areas. In injectable form, it’s often paired with a vasoconstrictor, a substance that narrows blood vessels near the injection site. This keeps the anesthetic concentrated in one area longer and reduces bleeding.
Benzocaine is the ingredient in most over-the-counter oral numbing gels and sprays. It works only as a topical agent, so you won’t encounter it in an injection. Products like Orajel, Anbesol, HurriCaine, and Cepacol all rely on benzocaine.
Several other anesthetics appear in dental settings. Articaine has become popular for its ability to penetrate bone tissue well. Prilocaine carries lower toxicity risk than lidocaine. Bupivacaine lasts the longest and is typically reserved for lengthy procedures expected to cause significant pain afterward, giving you a longer window of numbness during early recovery.
Common Uses at Home and in the Clinic
Over-the-counter oral anesthetics are most often used for minor, everyday mouth pain: canker sores, minor gum irritation, sore throats, and small injuries to the inner cheek or lip. You apply a small amount directly to the painful spot, and the area numbs within a minute or two. Relief typically lasts anywhere from 15 minutes to an hour depending on the product and how much saliva washes it away.
In clinical settings, the uses are broader. Dentists rely on injectable anesthetics for nearly every procedure that involves drilling, cutting, or extracting. Oral surgeons use them for wisdom tooth removal and implant placement. Doctors may spray an anesthetic into your throat before passing a camera down your esophagus. A prescription viscous lidocaine solution is sometimes used for widespread mouth sores caused by chemotherapy, radiation therapy, or certain infections, allowing patients to eat and drink with less pain.
How Long the Numbness Lasts
Topical gels and sprays produce the shortest effect. Most begin working within 30 seconds to 2 minutes and wear off within 15 to 45 minutes. Because saliva constantly dilutes the product, reapplication is often needed.
Injectable dental anesthetics last much longer. Lidocaine with a vasoconstrictor typically keeps the area numb for 1 to 3 hours, though soft tissue like your lip or tongue can feel numb for up to 5 hours. Bupivacaine can extend numbness even further, sometimes lasting 4 to 8 hours after the injection. That prolonged numbness is intentional for painful procedures, but it also means you need to be careful not to bite your cheek or lip before sensation fully returns.
Side Effects and Risks
Most people tolerate oral anesthetics well. The most common side effects from injections are temporary: numbness that lingers, minor soreness at the injection site, and occasionally a brief increase in heart rate from the vasoconstrictor. Topical products can cause mild stinging or a temporary change in taste.
The more serious risk associated with benzocaine is a condition called methemoglobinemia. This happens when the drug changes the structure of hemoglobin (the molecule in red blood cells that carries oxygen) so it can no longer release oxygen to your tissues effectively. Symptoms include bluish skin color, shortness of breath, fatigue, and confusion. In severe cases it can be fatal. A large study of nearly 28,500 patients who received benzocaine spray before a heart imaging procedure found the condition occurred in about 1 in 1,500 cases. While that’s uncommon, the consequences are serious enough that the risk deserves attention, especially with repeated or heavy use.
Lidocaine toxicity is possible if too much is absorbed into the bloodstream. For healthy adults, the maximum recommended single dose should not exceed 300 mg total, and doses should be spaced at least three hours apart with no more than eight doses in 24 hours. Signs of toxicity include ringing in the ears, a metallic taste, dizziness, and in severe cases, seizures or heart rhythm problems. Following the product’s dosing instructions closely prevents this in most situations.
Safety Concerns for Children
The FDA has issued a clear warning: benzocaine products should not be used for teething pain in infants and children under 2 years old. The agency found that these products provide little to no benefit for teething and carry a real risk of methemoglobinemia. This applies to all over-the-counter benzocaine oral products, including well-known brands like Orajel and Anbesol.
Lidocaine-based products are also not recommended for teething. For young children who do need oral lidocaine for other medical reasons (such as mouth sores), dosing is strictly weight-based and far more conservative than adult dosing. Children under 3 should receive no more than a tiny amount applied with a cotton-tipped swab, with at least three hours between applications and a maximum of four doses in 12 hours.
For teething pain, the FDA recommends non-medication approaches: a chilled (not frozen) teething ring, gently rubbing the baby’s gums with a clean finger, or a cold washcloth to chew on.
Tips for Safe Use at Home
If you’re using an over-the-counter oral anesthetic gel or spray, apply the smallest amount that covers the painful area. More product doesn’t mean faster or better relief; it just increases the amount of drug your body absorbs. Use a cotton swab or clean fingertip rather than squeezing gel directly from the tube onto your gums, which makes it harder to control the dose.
Avoid eating or drinking hot foods immediately after applying a topical anesthetic. Because you can’t fully feel the tissue, you risk burning yourself without realizing it. The same caution applies after a dental injection: wait until sensation returns before chewing, especially on the numbed side. Biting your cheek or tongue while it’s numb is one of the most common minor injuries after dental work.
If numbness from a dental injection hasn’t faded after 6 to 8 hours, or if you notice any signs of an allergic reaction like swelling, hives, or difficulty breathing after using any oral anesthetic, contact your dentist or doctor promptly.