This is the third installment in the Dental Local Anesthetic Allergy series. Part I talked about reactions to certain older style dental anesthetics which are basically not used in dentistry any more. Part II addressed allergic and sensitivity reactions to preservatives and other components found in some local anesthetics.

This now leaves us with what we call true allergies.  We use the term true to indicate it is a real allergic reaction to a dental local anesthetic – as opposed to a reaction to another component like sulfites – or other phenomenon.

Lidocaine – A Modern Dental Local Anesthetic

Lidocaine was first synthesized in 1943 and became widely available in the United States in 1948. Lidocaine was based on a new chemical structure of local anesthetics called amides. This class is chemically different than the previous “ester” ones such as novocaine and cocaine.

Lidodcaine with epineprhine is the most commonly used local anesthetic in the United States.

Immediately after its introduction, lidocaine took off in popularity for many reasons. One of the major reasons is because lidocaine did not cause allergic reactions with the frequency with which older anesthetics did. Because of this, the older class of anesthetics – novocaine included – were phased out – and by the 1980s basically no dentists in the United States were using novocaine anymore.

Allergies to Lidocaine and Other Amides

True allergies to lidocaine and other amide based anesthetics are rare. There is conflicting evidence on the prevalence of these reactions to lidocaine and other anesthetics.

• This 2013 paper documents a classic allergic reaction to lidocaine observed in a 12 year old child.
• This 2021 paper published in a prominent medical journal showed that of the patients referred to an allergy clinic for testing due to suspected allergies, only 3.5% were truly allergic.
• This 2012 paper published in a prominent British medical journal demonstrated that 1% of patients referred for testing showed a true allergy.

So, what might an allergy to the an injectable local anesthetic look like? Signs and symptoms could include:

• Pain and swelling at the injection site.
• Rapid heartbeat.
• Hives and/or itching (especially near the injection site).
• Cold/clammy skin.
• Nausea and possible vomiting.
• Wheezing and/or shortness of breath.
• A feeling of confusion and/or anxiety.
• And many other symptoms…

If/when this happens, it is best to get the opinion of the dentist/physician who administered the local anesthetic. He/she is the best equipped to identify a possible allergic reaction. From there, a referral for testing by an allergist may be recommended. If it turns out that you are allergic, there are options for how to receive dental care (read below).

Allergic vs. Adverse Drug Reactions

There mere sight of a needle can cause some people to pass out.

Other unpleasant reactions can occur after injections that are not allergic in origin. Generally speaking, those are called adverse drug reactions. These can include:

• A temporary rapid heartbeat and pounding in the chest. This can happen when epinephrine in the local anesthetic inadvertently leaves the injection site area and enters the bloodstream. It typically lasts a couple of minutes. If/when this occurs, you can ask your dentist in the future to use local that does not have epinephrine.
• Vasovagal syncope – a.k.a. – passing out.  This can occur before, during, or after the injection. You typically feel weak, can gave blurred vision, feel very hot, and can momentarily lose consciousness.
• Hyper responder/Reaction of Unknown Origin – in these cases, generally speaking, you over-react to the effects of the local anesthetic. The findings can include: blurry or blacked out vision, rapid and strong heartbeat, acute hypertension, sweating, nausea, and other signs/symptoms.

Dental Treatment with a History of Allergy or Significant Reaction(s) to Local Anesthetics

We are one of the few offices in the entire United States that is able to treat patients who are unable to tolerate local anesthetics, we typically see patients coming to us in one of 3 categories:

1. Those with a true allergy to one or more local anesthetic(s), confirmed by an allergist.
2. Those who experienced a reaction and are too scared/tired to do testing by an allergist.
3. Those who were tested by an allergist and experienced a severe but non-allergic reaction.

If you are one of these individuals, then you should not have local anesthetics administered to you. So what are your options:

• Get the dental treatment done without any local anesthetic. This can be quite uncomfortable though, as you can imagine.
• See a dentist who can provide dental treatment using Benadryl (diphenhydramine) as a local anesthetic with IV sedation. This is the technique we employ in our office and we have patients from all over the Northeast coming to see us. You can learn more here.
• As a last resort, the dental procedures can be done under general anesthesia. But there are many drawbacks to this approach.

Final Thoughts

So, over three separate posts, we’ve pretty much covered nearly everything there is to know about allergies to dental local anesthetics. As mentioned above, we offer treatment options that avoid the use of “-caine” local anesthetics. If you are interested, it is best to read about our approach here, or call us (203) 799 – 2929 or visit this page to request an appointment.

In Part I of this series, we covered allergic reactions to ester based local anesthetics used in dentistry. These occur very rarely now because the entire class of ester local anesthetics has essentially been phased out in favor of amide based local anesthetics. Nevertheless, allergic reactions can and do occur after the “novocaine shot.” So the question is, what is/are producing the reactions?

Methylparaben

Methylparaben

Methylparaben is a preservative used in the pharmaceutical, personal care, and food industry. It is found in many cosmetics currently on the market in both the United States and elsewhere. Methylparaben was at one point included as a preservative in dental local anesthetics. Its main function was to inhibit the growth of bacteria and to help maintain the sterility of the anesthetic.

Methylparaben is chemically very similar to PABA – the metabolic by-product of many ester-type local anesthetics. As outlined in Part I of this series, PABA can produce allergic reactions in some individuals. Because of this similarity to PABA, when methylparaben is injected as part of a local anesthetic, allergic reactions can occasionally occur.

Because of this, since the mid 1980s, the U.S. Food and Drug Administration mandated the removal of methylparaben from single use dental local anesthetic cartridges. As a result, unless the dentist is using local anesthetic from a multi-use container (which is incredibly unlikely in your typical private practice in the U.S.), you will not be exposed to methylparaben as part of the local anesthetic injection.

Methylparaben listed as a preservative in 1% lidocaine. This type of local anesthetic is typically only seen in hospitals and physician offices.

Many multi-use vials of local anesthetic still contain methylparaben – as seen above. But those are typically seen in hospital settings and in individual physician offices.

Sulfite Sensitivity

Lidocaine with epinephrine – used in dental offices – has sulfites.

Sulfites are a class of chemicals used a preservatives. Like methylparaben, sulfites are used in a variety of ways. They are most commonly used to preserve food and can frequently be found in wine, jams, some frozen seafood, and many other products.

In dentistry, sulfites are added to local anesthetics that contain epinephrine. The sulfite – most commonly seen as potassium metabisulfite – is used to prevent the breakdown of the epinephrine. This allows the local anesthetic to have a shelf life of more than a year.

Exposure to sulfites in food as well as a “novocaine shot” can provoke allergy-type symptoms in susceptible individuals. If you have asthma, you are much more likely to be sensitive to sulfites than non asthmatics.

Bupivicaine – marketed under the brand name Marcaine – showing Metabisulfite as an ingredient.

So what would an allergy to sulfites look like? The reaction would have all the hallmarks of a systemic reaction to an allergen. In this article, a patient was injected repeatedly on one side with a dental local anesthetic containing metabisulfite. Within a day, she was experiencing mild swelling at the injection site. After a couple of days, she experienced severe facial swelling with pain and was admitted to the hospital. Allergy testing later concluded an allergy to bisulfite found in the local anesthetic.

What to do if You’re Allergic to Sulfites

So, if you suspect you may have sulfite sensitivity, be sure to ask your dentist to use a local anesthetic that does not contain epinephrine. Dental local anesthetics that do not contain epinephrine do not have metabisulfite.

Carbocaine does not have epinephrine – so it does not contain any sulfites

There is an important distinction between sensitivity to sulfites and allergic reactions to sulfites. The Cleveland Clinic has a nice summary located here.

Note that sulfite sensitivity and sulfa-drug allergies are totally different! So if you have an allergy to sulfa drugs – more formally known as sulfonamides and includes the brand name Bactrim – it does not mean you are allergic or sensitive to sulfites. And vice versa. The reference is located here.

So what’s next in Part III? We’ll cover true allergies to dental local anesthetics – which are extremely rare but are possible.

This will be the first of a three part series covering the various types of allergies associated with dental local anesthetics (frequently referred to as “novocaine”). Why write this? Well, some of the most frequently used search terms that cause people to arrive at our site are some combination of “allergy” and “novocaine.”

Over 1 million injections of “novocaine” are administered in dental offices in the United States each year.

Over the years, we’ve observed that many of our own patients think they may be allergic to the local anesthetic used at the dentist. This is not surprising given that over 1 million local anesthetic injections are administered each year in dental offices in the United States. With this level of frequency, adverse events are bound to happen, some of which may be interpreted as allergies.

The three parts are:

1. The Esters (this article)
2. Methylparaben and Sulfites (part 2)
3. True amide allergies (part 3)

The titles of the three parts may appear cryptic, weird, or just plain boring. But this is how it needs to be organized. We’ll start with a brief history of local anesthetics.

Cocaine and Procaine

Believe it or not, cocaine was the first local anesthetic used in dentistry. Cocaine was first used in a dental procedure as an injectable local anesthetic in 1884. While it was an effective anesthetic, there were unwanted side effects (euphoria, cardiovascular stimulation, addiction, etc.).

Yes, you could purchase cocaine legally back in 1885. And for only $.15

In 1905, another anesthetic was synthesized called procaine. It had all the anesthetic properties of cocaine but none of the undesirable side effects. Because of this, it was very quickly adopted, and a brand name version of procaine – novocaine – was launched. Novocaine was classified as an “ester type” anesthetic.

So What is an Ester?

The chemical symbol of an ester.

An ester is a term from organic chemistry that describes a specific part of a molecule. The diagram here is not that important.

The important concept is that cocaine, procaine (brand name novocaine), and many other dental local anesthetics are considered “ester type anesthetics.” They are given this name for two reasons. First, there’s the obvious reason: they all contain an ester group. The second reason is to differentiate them from another family of local anesthetics called “amide type anesthetics.”

Allergies to Ester Based Anesthetics

Now we actually get to what everyone wants to know. And that is to begin talking about allergic reactions to dental local anesthetics. We begin with ester based local anesthetics because at one point these were the only local anesthetics available. Read on:

• When ester based local anesthetics are injected into the body, they are metabolized into a chemical called para-aminobenzoic acid (also called PABA).
• PABA is known to cause allergic reactions in some people. So, back when novocaine was actually being commonly used (from 1905 to the mid 1950s), patients frequently experienced true novocaine allergies.
• Because of the documented allergic reactions to PABA – caused by injections of ester based local anesthetics – ester based injectable dental local anesthetics stop being used in the United States. Novocaine was last sold in the United States in 1982.
• What is used instead? You guessed it – amide type anesthetics.
• Ester based local anesthetics are only used in dentistry in the U.S. as topical anesthetics (also known as numbing jelly). The most common one is benzocaine.

So, to summarize, true novocaine allergies exist, but they do not occur anymore because novocaine is no longer used.

But what about allergies from other sources? What does a true allergy look like clinically? Those will be covered in parts 2 and 3.