Benzocaine Side Effects

Benzocaine side effects can include skin reactions, red eyes, sore throat, fever and cyanosis (a bluish tinge of the fingernails, lips, skin, palms or nail beds). Skin reactions may present as burning, stinging, blistering, swelling or flaking. Allergic reactions are also possible.

Some patients develop methemoglobinemia, a serious and potentially life-threatening condition, when taking benzocaine. The drug is no longer recommended for oral use in young children due to this possibility.

As of September 30, 2024, the most common side effects reported to the Food and Drug Administration’s Adverse Events Reporting System were due to oxygen deprivation. These conditions included methemoglobinemia, cyanosis and difficulty breathing. Methemoglobinemia had the most reports, making up 32% of the total side effect cases reported.

Disclaimer: Reports sent to the FDA don’t necessarily mean the drug caused an adverse event. Consult a health care professional before stopping or changing medication.

The cases reported to the FDA may not provide a full picture of benzocaine’s safety. They represent only drugs specifically listed as benzocaine. This can exclude other formulations that aren’t listed as benzocaine but contain it. You should be aware of the risks of topical anesthetics containing benzocaine before using them.

Common Benzocaine Side Effects

Localized skin reactions, nausea and vomiting are some common benzocaine side effects. These effects are typically mild and temporary.

Other side effects, like skin discoloration, headache and fever, can signal a serious reaction. Specifically, cyanosis may indicate low blood oxygen levels associated with methemoglobinemia.

Some patients who use benzocaine products develop a serious reaction called methemoglobinemia. This complication is more likely with higher doses.

Allergic reactions are another possible serious benzocaine side effect. Severe allergic reactions can cause anaphylaxis, which is sometimes fatal, or contact dermatitis. Contact dermatitis can cause skin to slough off and become infected.

In one case study published in BMJ Case Reports, a man suffered gangrene and required a skin graft after using a 5% benzocaine product.

Notify your doctor if you notice symptoms such as difficulty breathing, skin discoloration or signs of infection. They could indicate a serious health condition that requires medical attention.

Benzocaine and Methemoglobinemia

Some patients develop a potentially fatal complication called methemoglobinemia after using benzocaine. This condition causes elevated levels of methemoglobin in the blood. Methemoglobin is a type of protein that cannot bind to oxygen, so excess levels reduce the amount of oxygen carried through the blood. Left untreated, this can cause coma or death.

There have been some lawsuits concerning methemoglobinemia and benzocaine, but none were widespread.

When To Seek Medical Attention

You should seek medical attention if you notice any symptoms consistent with methemoglobinemia. These symptoms grow more severe as methemoglobin levels increase in the blood.

At methemoglobin levels around 10%, you may notice early signs of cyanosis, such as a bluish tinge to your skin. At 20%, symptoms including anxiety, headaches and light-headedness may develop. Confusion and loss of consciousness can happen with methemoglobin levels between 30% and 50%. Once they cross 50%, the risk of seizures and coma increases. There is a heightened risk of fatality at levels above 70%.

In 2018, the FDA announced a stronger warning about the risk of developing methemoglobinemia. The announcement revealed the FDA estimated that over 400 patients developed methemoglobinemia after using benzocaine.

The agency also advised against the use of benzocaine in teething products for young children. The FDA concluded that the risks to young children outweighed the benefits of using benzocaine. They required drug manufacturers to stop marketing benzocaine teething products for children under the age of 2.

With this announcement, the FDA took steps to ban benzocaine in products for infants and young children. It also required a warning about the risk of methemoglobinemia in all prescriptions containing benzocaine. The agency recommended that manufacturers of over-the-counter products standardize warnings across product labels.

Multiple topical anesthetics are safe and effective alternatives to benzocaine. If you have a benzocaine allergy, you may be able to use several other topical anesthetics on the market. For example, lidocaine is a similar but stronger medicine than benzocaine. So, it needs a lower concentration to be effective.

However, not all versions of these medications are appropriate for all body parts. There are many versions of local anesthetics, ranging from creams, rinses and injections. Be sure to read the label thoroughly before using any new medications.

Local anesthetics work by blocking pain receptors from sending signals to your brain. According to VeryWellHealth, many local anesthetics end with “caine” due to having a chemical structure similar to cocaine. However, unlike cocaine, these drugs are not addictive, nor do they raise blood pressure.

For pain relief from infant teething, doctors generally recommend drug-free alternatives. These include massaging the gums and using a firm rubber teething ring.

According to the Professional Home for Oncology Nurses, a saltwater and baking soda rinse can promote oral health and relieve mild pain from mouth sores. Be sure to use the correct ratio: 1 teaspoon of baking soda and 1 teaspoon of salt for every 4 cups of water.

Editor Lindsay Donaldson contributed to this article.