Dental MythBuster #14: A Swollen Lip After a Dental Visit Means You’re Allergic to Novocaine

This is one dental myth that every dentist has to deal with at some point. And that is the myth that if a child’s lip swells up after a dental visit where local anesthetic was used, it always means the child must be allergic to something the dentist injected.

And to make matters worse, this myth is then often propagated by the child’s pediatrician.

What would you think if you saw this the day after your 8 year old got a filling on his lower right molar:

swollen lip from biting while numb after filliing

Lower right lip swollen after a filling was done on the lower right.

That looks pretty nasty right? Something clearly happened here. In my own experience, and in talking to other dentists, parents generally do one of four things upon seeing this:

  1. Parent immediately heads to the closest ER or emergency walk-in clinic.
  2. Parent immediately calls the pediatrician for an emergency appointment and is seen that day.
  3. Parent gets on Google, becomes almost immediately convinced of an incredibly dire situation, and then does either #1 or #2.
  4. Parent calls the dentist office.

Wouldn’t it make sense to call the dentist office? After all, it was the dentist who did the procedure, wouldn’t he/she know what is going on?

But unfortunately, options 1, 2, and 3 are often pursued. And in many of those cases, an incorrect diagnosis is frequently made, which leads to unnecessary finger pointing, as well as wasted time, confusion, and missed school for the child.

So, what does it mean when the lip swells up after a dental appointment when local anesthetic was used?

Swollen Lip = Lip Biting While Numb (99.99% of the time)

Here are two cases I’ve seen in my office:

swollen lip after dental work means lip biting

Swollen lips after dental work. Both patients admitted that they inadvertently bit and/or played with their lips while numb.

The above photos look unpleasant, right? In both cases, lower teeth were given local anesthesia, and that numbness extended to the lip. And in both examples, the patients admitted to repeatedly biting their lip.

The repeated biting led to swelling, bleeding, and bruising. Many times, the child has no recollection of doing it, because the child was numb and felt no pain. But the next day – whoa!

It is quite easy to see how this can come from biting. Go ahead and try to bit your lower right lip with your upper front teeth. Easy, right? Do this a couple of times very hard while you’re numb and you’ll end up looking like the one of the photos.

Why This is not an Allergy

Despite seeing this on a regular basis, many dentists (myself included) still have to deal with accusations and/or false diagnoses of allergies from the injection. Here are some key points:

  • Location. The injection site is nearly always located far away from the traumatized area – in some cases nearly two inches. If it were an allergy, why then is the injection site totally normal? See the photo below.
  • Appearance. In general, allergic reactions do not produce a localized ulcerated area away from the injection of the alleged allergen. The appearance of this is simply not consistent with an allergic reaction.
  • Lack of Systemic Symptoms. Even less severe allergic reactions will produce other symptoms such as dry mouth, hives, and other findings. None of these are typically present in lip biting.
dental injection photo next to tooth

Dental injection adjacent to a 12 year molar. How could this produce an “allergic” reaction on the lip only when the injection site is so far away?

Of course, allergic reactions can occur from the injection. However, they are exceedingly rare, and don’t present like this. For more information, see this three part series.

What Should You Do?

So, if you or your child’s lip is swollen after receiving local anesthetic, what should you do? Call your dentist. Generally speaking, pediatricians, PAs, and NPs do not have experience seeing these types of things, and then come up with what we call “creative diagnoses” which are usually incorrect. General dentists and pediatric dentists see lip biting all the time and can guide you on how to handle it.

But to stress this point, it is a myth that a swollen lip (in the absence of other findings) after a dental visit means you are allergic to lidocaine (mistakenly called novocaine).

Until the next dental myth is busted…

More on the Fabled “Epinephrine Allergy”

Ever since I posted Dental MythBuster #10 – I’m Allergic to Epinephrine back in November 2013, I have observed its growing popularity. But much to my surprise, the “epinephrine allergy” post generated a tremendous number of comments and emails which attempted to refute my assertions and/or attack me personally. In fact, one email even threatened physical harm!

photo of epinephrine where people believe they are allergic

Many believe they are allergic to this.

I had no idea that I would strike such a nerve. Apparently, there are many individuals out there who are convinced they are allergic to a substance that has been running through their bloodstream since before they left their mother’s uterus. And they will stop at nothing to attack, ridicule, or even threaten anyone who might suggest otherwise.

While I generally attempt to stay away from the more controversial dental topics out there (like public water fluoridation or amalgam fillings containing mercury), I do feel compelled to publish additional facts and data to support the fact that an epinephrine allergy does not exist!

You Could be Reacting to Sulfites or Latex

Many individuals who claim to have an epinephrine allergy learn, either through an allergist or through my blog, that their post-injection symptoms were caused by either sensitivity or allergies to two components found in most dental injections: sulfite preservatives and/or latex.

Sulfites found in local anesthetics and red wine can give you allergic reactions.

Sulfites are found in most red wine and in local anesthetics containing epinephrine.

Sulfites are used to preserve epinephrine in dental anesthetics. Sulfites can provoke severe sensitivity reactions in certain individuals. If you receive a dental injection with sulfites and you are sensitive to it, the reaction can closely resemble an allergic type response (for in depth details on sulfites and dental local anesthetics, see this post I published).

On the tip of every dental local anesthetic carpule is a tiny piece of latex. Studies have shown that the latex allergen can enter into the local anesthetic solution when that latex is pierced for an injection. But those same studies also show no reports of an allergic reaction due to the latex. (Study info: Shojaei AR, Haas DA. Local anesthetic cartridges and latex allergy: a literature review. J Can Dent Assoc. 2002;68:622-626.)

I mention all this to demonstrate that there are at least two chemicals in the injection which could potentially cause an allergic type response. But it’s not the epinephrine!

It’s Documented in Textbooks and Articles

Many readers of my first post simply attacked me personally and stated that I was wrong. Others wanted proof. Here is a screen shot from an online article:

Article proving that an allergy to epinephrine does not exist

This screen shot is from this article in the magazine Dentistry Today. It says “allergy to epinephrine cannot occur.” It can’t get any more clear cut than with that statement!

Need more proof? In the book a Handbook of Local Anesthesia by Dr. Stanley Malamed, he writes:

Allergy to epinephrine cannot occur in a living person.

This is on page 320 from the 5th edition.

Why isn’t an Epinephrine Allergy Listed on the Drug Insert or Prescribing Information?

After tobacco companies, pharmaceutical firms are probably the biggest litigation targets out there. Haven’t we all seen ads on TV looking for plaintiffs to sue drug companies? Ever hear of the website 1800baddrug.com?

Naturally, drug companies list all the known adverse effects on the drug sheet. If they don’t list something, and then an event occurs, the attorneys will have a field day! So if an allergy to epinephrine existed, wouldn’t it be listed on the drug sheet?

penicillin lists an allergic reaction as a  risk

Unlike epinephrine, the insert for penicillin mentions the risk of allergy.

Look at the drug inserts for these common medications: Zithromax (Z-Pak), Penicillin, Bactrim

On all of these, you will see mentions of allergic reactions. This indicates that known allergies can occur after taking the medications.

Now look at the prescribing information for all these forms of epinephrine: Epinephrine Auto Injector, Epi-Pen, Epinephrine Injection.

None of them mention an allergy to epinephrine (note that some mention a reaction to the sulfite).

So I’ll pose the question again: if an allergy to epinephrine existed, wouldn’t it be listed on the drug sheet? Why would the drug companies fail to include it knowing they could potentially be sued over its exclusion?

Note that I’ve used the terms Drug Insert and Prescribing Information quite liberally here. There are many variations depending upon who it is for (consumer vs. prescriber), but it is the FDA-required document that pharmaceutical companies must publish.

Show us a Mechanism

If you’ve made it this far, and you’ve already read my first post, you’ve hopefully learned that an allergy to epinephrine is not possible. But for those determined skeptics, I’ll make this request:

Please provide a plausible mechanism for how you can be allergic to a chemical that has been in your bloodstream since before birth and is currently being synthesized and released in your body as you read this.

Should you wish to post comments on this article, I will ask politely that you refrain from profanity and/or personal attacks. And if you read this and your heart starts to race (either because you’re angry at me or you’re excited with what you learned), that’s because of the adrenaline being released into your bloodstream… to which you are not allergic!

Novocaine Allergy Part III – True Amide Allergies

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

This now leaves us with what I call true allergies.  I use the term true to indicate it is a real allergic reaction to a dental local anesthetic – as opposed to an adverse reaction or other phenomenon. I stress this distinction because allergic reactions to modern local anesthetics are extremely rare.

Lidocaine – A Modern Dental Local Anesthetic

lidocaine local anesthetic with epinephrine used at the dentist

Lidocaine with Epinephrine is the most common formulation in the U.S.

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 ones such as novocaine and cocaine.

Immediately after its introduction, lidocaine took off in popularity for many reasons. One of the reasons is because lidocaine did not cause allergic reactions the way 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.

Allergic to Lidocaine?

True allergies to lidocaine and other amide based anesthetics are exceedingly rare. There is conflicting evidence on the prevalence of these reactions to lidocaine and other anesthetics. A prominent 2009 article in the journal Anesthesiology says “allergic reactions to amide local anesthetics remain anecdotal.” A 2013 article published out of Saudi Arabia documents a case study of a true lidocaine allergy in a 12 year old. According to this 2002 paper, an individual with an allergy to one amide does not mean he/she will react to others. Any Google search will yield thousands of results – some from prominent medical journals with sterling reputations – and others from individuals posting their experiences and assumptions.

lidocaine and articaine both amide type local anesthetics

Most experts agree that in the cases of true allergies to lidocaine, other local anesthetics such as articaine can be used (assuming proper testing first).

The current consensus in the dental community is that true allergies to amide based local anesthetics are possible but very rare. As a patient, you have much better odds of being struck by lightning than experiencing an allergic reaction to lidocaine!

If you are injected with a local anesthetic and are allergic, what would happen? You would likely exhibit all the classic signs of an immediate type reaction: generalized swelling, itching, urticaria (hives), possible respiratory difficulty, and many other signs.

But remember, only a qualified allergist can diagnose you with an allergy.  Neither I nor any internet site can tell you definitively.

Events where you think you are allergic but are not!

I’ve witnessed firsthand hundreds of incidents where a patient thinks he or she is allergic when in reality something else is occurring. These incidents include:

photo of epinephrine which is used at the dentist in local anesthesia

A racing heart does not mean you are allergic to epinephrine!

  • A racing heartbeat (tachycardia) occurring immediately after a dental local anesthetic is administered does not mean you are allergic to either the local anesthetic or the epinephrine in it. This is a dental myth I busted here.
  • If you start to feel faint and break out in a cold sweat and nearly pass out immediately after an injection, this is most likely vasovagal syncope (and not an immediate allergic reaction).
  • If you do exhibit signs of an allergic reaction, you are far more likely to be reacting to a preservative in the local anesthetic than you are to the actual local anesthetic. The most common culprits are methlyparaben and metabisulfite.

Dental Treatment with a Documented Amide Allergy

If you are one of the rare individuals with an amide allergy confirmed by an allergist and you need dental treatment, what are your options?

  • Get the dental treatment done without any local anesthetic. I do this periodically for my own patients who don’t like the feeling of being numb. But this would only work for minor procedures, not for major ones such as extractions or root canals.
  • Have the allergist test to see your response to other amide local anesthetics. Many papers in the literature talk about individuals reacting to one amide but not another.
  • Benadryl (diphenhydramine) can be used as a local anesthetic when injected. While not as effective as amides, it can offer some degree of local anesthesia. But check with your dentist – very few dentists are prepared to do this and would need advance notice.
  • As a last resort, the dental procedures can be done under general anesthesia.

Final Thoughts and a Disclaimer

While true allergies are rare, they can and do occur. But don’t assume. An adverse or unexpected reaction does not mean you are allergic!

And as mentioned in both the sidebar and footer of this website, this article is for informational use only and is not intended for medical advice. Please consult your physician if you believe you have an allergy and always discuss this with your dentist prior to having any dental treatment performed.

Novocaine Allergy Part II – Methylparaben and Sulfites

In Part I of this series, I covered allergic reactions to ester based local anesthetics used in dentistry. These occur very rarely now because the entire class of ester local anesthetics have 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

chemical structure of 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 I 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.

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

Since I have never used a dental local anesthetic with methylparaben in it, I have never seen an allergic reaction firsthand.

Sulfite Sensitivity

Sodium metabisulfite used as a preservative in dental local anesthetics

The label from a box of lidocaine with epinephrine used in my office in Connecticut. Metabisulfite is a component.

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.

So what would an allergy to sulfites look like? I personally have never seen one. 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.

Bupivacaine with epinephrine using metabisulfite as a preservative

Box of bupivacaine showing sodium metabisulfite as a component.

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.

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 have been found.