5 Reasons You Can’t Get Numb at the Dentist

As a dentist in private practice, I hear stories ALL the time about patients who “couldn’t get numb at the dentist.” Not surprisingly, many of the comments that readers post here on this site also deal with this very issue.

In response to this, I decided to compile a Top 5 list of reasons for why this happens. So here goes:

1. You have an infection
dental abscess on gums showing infection with pus

This tooth was difficult to get numb because of the infection in the gums above the tooth!

Sometimes, a patient comes in with an active infection and it can be difficult to get them completely numb. This is obviously very frustrating for both the dentist and the patient. Why does this happen?

An active dental infection will usually result in the presence of pus. In most cases, the pus is acidic. Conversely, dental anesthetics (lidocaine, novcaine, etc.) function best in slightly basic environments. The end result is that the unique chemistry of the infection “deactivates” the local anesthetic, making it so that more anesthetic is needed. And in cases of severe infections, sometimes you simply cannot get the patient 100% numb.

2. You moved during the injection

Let’s face it – some injections – but not all – hurt! And it just so happens that the one that hurts the most is the one that requires the most patient cooperation. I speak from experience having done this well over ten thousand times.

large dental needle for nerve blocks to get numb

We have to sink this needle deep into the tissue. If you move, it is easy to miss the target. Paper clip is for scale.

For lower back teeth, we nearly always need to do a nerve block.  This is where we have to go deep through muscle and other tissue and deposit the local anesthesia near the nerve. We can’t actually see the nerve – we have to use various anatomical landmarks to guide us to the area.

If you move suddenly, the needle will also move.  Most often, it will have moved away from the nerve! So we then end up depositing the anesthetic farther away from the nerve than we would like. What happens next? You don’t get numb. Fortunately, if we have to administer a second injection, it will rarely hurt, and then we can place it spot on.

On rare occasions – and this has never happened to me nor most dentists – you can move so much that the needle can actually break!

3. I am not using epinephrine

I’ve blogged about this before. Epinephrine is added to dental local anesthetics because it enhances the numbness. How does it do this? Epinephrine acts as a vasoconstrictor and reduces blood flow in the area of the injection. The end result is that the local anesthetic stays around much longer and gives a more profound feeling of numbness.

marcaine dental anesthetic with epinephrine

Marcaine with epinephrine. The epinephrine will allow for a more profound level of local anesthesia

In certain circumstances, we use a local anesthetic that does not contain epinephrine. Why? Patients with certain cardiac conditions or who take certain medications are best served with one that does not contain it. Others have experienced a mild adverse reaction (some mistakenly think they are allergic to epinephrine) and prefer we don’t use it. A small fraction of patients are allergic to the sulfite preservative so we can’t use it in those cases either.

If we can’t use epinephrine, there is a chance you won’t feel numb enough. Or we’ll have to re-inject multiple times.

4. You’re wired differently

The human body is incredibly variable. People are double jointed. Remember the kid in grade school who could move his ears? Why is Usain Bolt faster then any other human? You get the picture.

Do you think your nerves look like the drawing below?

Mandibular nerve diagram showing nerves and numbing for lower teeth for the dentist

Nerves going to lower teeth. Each person is different!

If you answered yes, then you’re probably wrong!

Most people have what I might call “standard anatomy.” This means that the nerves going to your teeth are where you might expect them to be located. But just like Usain Bolt and the kid from fifth grade who could move his ears, some patients have extreme variability with the nerves going to their teeth. We see this most frequently with lower molars.

Some people may have up to 4 nerves going to their lower molar teeth. This can mean 4 different injections to get them numb! This doesn’t mean your dentist is incompetent – it means you’re wired differently. So if that happens to you, just think about Usain Bolt and the kid from fifth grade who could move his ears.

5. You have red hair

Joan from Mad Men has red hair and can't get numb at the dentist

Joan from Mad Men would have difficulty getting numb!

I’ve blogged about this on two separate occasions – here and here.

But to summarize, people with red hair have a built in resistance to local anesthetics. This means that more local anesthetic is required to achieve profound numbness in those people with red hair. The reason behind this is complex, but the genetics for red hair also confers resistance to local anesthetic.

I can say definitively that from personal experience, redheads nearly always require more local anesthetic. All of my red haired patients are aware of this – and we joke about it each and every visit!

Want to see reasons 6 through 10? Here they are!


  1. Heather says:

    It’s hard for me to get numb and oddly enough, I was born with red hair, but it turned blonde by the time I was a year old.

  2. This just happened to me today – 3 novocain shots, the entire side of my face was numb but I felt everything the poor dentist tried to do on my lower molar. Rescheduled for another time. Hopefully, he can get that novocain to the right spot next time. 🙁

  3. Bill payne says:

    Ehlers danlos=resistance to local anesthetic!!

    • Bill,
      You are correct about Ehler Danlos. But remember, there are MANY variations of Ehler Danlos, and NOT ALL will result in a resistance to local anesthetic. I will be publishing another post about this.

      • I had an unsavable 1st bicuspid extracted, no infection but a big cavity, it took the doctor about an hour and 6 shots. Need less to say each shot after the first was because of nerve pain. She never gave up. I’ve had a few others pulled over the years and always had trouble getting numb. Years ago I had another DDS give up and referred me to a surgeon. I don’t have red hair but grandma did and we’re Swiss/German.
        Is there a test to detect this resistance ?
        Thanks for your time…..

        • There are a ton of other variables to consider before thinking you are resistant. I outlined 10 in the 2 blog posts and there are other factors not even listed.

        • Menotnumb says:

          I do not have red hair but my mother, sister, and daughter do. My grandparents on my father’s side were both Swiss. No one in my husband’s family have has red hair. I recently had a tooth removed because I cracked it. I told the doc that people have trouble getting me numb. And he kind of shrugged it off. That was until he started. An hour and a half in I was still talking normal, but my noise was numb. He was completely beside himself. I also have woken up during surgery. I thought it was interesting the correlation between the red and Swiss.

  4. I am a redhead… I went to the dentist for extreme pain on a tooth on the top right side tooth (3rd tooth from the front right tooth), the dentist started a root canal – he removed 2 nerves with no problems – went back 5 days later to have the root canal completed – 4 shots later, I could still feel him trying to clean the tooth out. He put me on penicillin for 7 days as he thinks I now have an infection – I am into day 4 of the anti, and I’m still experiencing pain – what are the odds that the dentist will be able to get me numb enough to complete the root canal 4 days from now? Should I be going to an endodentist vs. a local dentist?

    • Tina,
      This will occasionally happen. The fact that you got numb the first time suggests it has less to do with you being a redhead and more to do with a possible infection. There many general dentists who are just as skilled at performing root canals as endodontists, so I can’t really answer that question.

  5. I went in today to have a filling redone and a crown on a tooth that has been cold sensitive for some time. It is a molar on the lower left side. I was given 3 injections which resulted in my left side of my face being numb but could still feel cold on the tooth. So she told me it was due to having caffeine this morning so we reschedule the procedure.I have never had this problem before or have I ever heard of caffeine causing this. I’m not sure what to do next. Any suggestions?
    PS not a red head

    • I’ve done a fair amount of research on this subject and my conclusion, and this is mine alone, is that there’s no real evidence to suggest that caffeine alone can significantly affect your ability to get numb. The “bible” of all textbooks on local anesthesia in dentistry (Handbook of Local Anesthesia by Malamed) has no mention of this phenomenon.

      Caffeine can affect the vascular system which, in some cases, could theoretically cause the local anesthetic to travel away from the site of action. But that can likely be overcome by using a local anesthetic with a vasoconstrictor.

      In your case, you have a lower molar, which can be notoriously difficult to numb due to variable and complicated anatomy. As I’ve posted before, there can be sometimes 5 different nerve branches that can affect a lower molar. I suspect your dentist simply did not get local anesthetic around one of those nerves.

      That doesn’t mean your dentist is incompetent; it happens to everyone. I treat many “hard to get numb patients” and for lower molars, we sometimes have to spend 30 minutes with 5 different injections just to get them numb. Patience and a methodical approach to anesthetizing all the nerves is what it takes in nearly all the cases I see.

  6. Shannon Kreis says:

    Can you give advice to people who are resistant to locals? I’m a redhead as well and I just had yet another painful experience. I told the dentist I have had trouble getting numb and not just at the dentist. My dermatologist doesn’t like having to give me locals, either. I think he took my concerns into account and was very thorough in the initial injections. During my two fillings, I didn’t feel like the dentist believed that I could still feel pain. I even felt the subsequent injections he did when we were halfway done (I’m pretty sure he hit bone but not sure if it was intended or not) I couldn’t sit still for him to drill. He was trying to rush through and just get it over with and it hurt badly. I felt embarrassed and guilty, like it was my fault I wasn’t numb. I was in tears when it was over and I have a fairly high pain tolerance. How can I communicate to the doctor in a way that he or she will understand? My words don’t seem to be sufficient.

    • Shannon,

      Sorry about your negative experiences. If you were to poll 100 dentists about redheads, I would suspect that less than 20% are aware of this phenomenon, and likely much fewer.

      The key, in my opinion, is open communication. It is possible your dentist does not know about the redhead phenomenon. I talk to all my redhead patients about this.

      You should go ahead and communicate your concerns in advance of any appt that would involve local anesthesia. I have many patients – not just redheads – who are difficult to numb (I attract lots of “tough to numb” patients because of this blog”). In those cases, we have them come in a half hour early, I administer special type(s) of local anesthetic, we have them relax, and usually we can get things done after waiting enough time. It all comes down to open communication.

      I doubt your dentist was enjoying himself. He was probably just as frustrated as you. If the two of you can come up with a plan, then it should hopefully work out.

  7. Tabitha Brown says:

    I went to the dentist about 2 months ago for a filling. She numbed me without any problems. However, after the procedure about 3 weeks later I still felt sensitivity so I went back so she could adjust the filling and she tried 5 different shots and I couldn’t get numb. My face was numb but each time she blow air or water I felt it. So I left feeling discouraged and was planning to leave her, but another dentist told me that sometimes that just happens so to give her another try and I did on last week and I got numb with no problem at all. This was my first time ever experiencing anything like that. Hope it never happens again.

  8. Chelcea Farrar says:

    I’m red headed. And I have to get three shots (well every visit of mine I’ve gotten 3) and I can still feel it but it’s not really pain. It is true here

  9. How would I go about finding a dentist that would be able numb my tooth before drilling. My present dentist has filled several small filling and 2 crowns which all hurt some more than others. I think the routine has been to give me 3 shots waiting sometime in between each one to see if it works then saying I have to tough it out. And I end up crying and making him stop several times. I just can’t do this any more. I never had any issue until about 14 years ago when I had a tooth pulled and they couldn’t numb it and had to give me gas to get it out. Still hurt but I honestly did not care cause of the gas. My face gets numb like a pervious poster but not the tooth. Thank goodness I am not at the dentist as much as my husband. But I am having an issue with a tooth right now and have an apt in a couple days. I told them when I called that I just don’t think if he needs to fill any thing that he’ll be able to touch this one without numbing it. She said I needed to talk to him which I have everytime but hes told me sometimes people that have high blood pressure have issues which I don’t usually although now going through all those times not being numbed I can’t imagine it doesn’t spike now. Anyway he also gave some other reasons which none applied to me except maybe having a square jaw and my nerves being a little different than normal. But I take issue with that unless nerves can shift and move cause as a child I had a lot of major fillings done ( chewed a lot of that big fat sugar filled bubble gum ) and like I said up until I got that tooth pulled never had any problems. Anyway the person I talked to said they couldn’t do anything else for me short of knocking me out. So I thought maybe it’s time to start looking for another dentist but I would like to find one that know how to deal with this type of thing and one that excepts my insurane . So any suggestions, ideas or advise on how to go about this would be Super Appreciated. Thank you .

  10. I just left my dentist office. I have a cracked uper left molar that needs to come out. I told him I’ve had several traumatic experiences with dentists drilling without my tooth being numb. Years ago I found a great dentist who told me my nerves are “wired differently”. He was able, after several atempts to numb the correct tooth. Today I tried to explain this to my current dentiat but he wasn’t hearing me. He had given me 3 shots of a local anesthetic. My left ear, cheek & eye socket were numb but every time he touched that tooth I could feel it. He insists it must be an infection. I’ll take the antibiotics as prescribed to rule that out. But despite 3 shots I could still feel my entire upper left lip and each of those teeth in the upper left of my mouth. I have another appointment for the extraction after I finish the antibiotics. Is there something I can say to get him to pay better attention to the “wired differently” issue? It is so frightening and frustrating to have to use a specific dentist for insurance purposes but not have him listen.

    • Faith,
      I understand your frustration. It could be a lot of factors – infection, your nerves, poor technique.
      When I have a patient who I know is tough to get numb, we have him/her come a half hour early. I administer extra local and then let them sit and relax while we give it plenty of time to work.
      You could also inquire about a relaxing pill to take beforehand and/or nitrous.

      • christina says:

        My dentist does that for me. He is very calm and kind. He knows how hard I am to numb, and always schedules extra time so I am not anxious and can give the extra shots time to work. You sound like a lovely dr. 🙂 Thats why I have been with the same dr for 11 years!

  11. Ever since I was 10 and saw my first dentist I’ve had trouble getting numb. I unfortunately have bad genetics for my teeth and although I brush and floss daily I’m 22 and currently had around 10 crows, most of my teeth filled and one route canal in an infected front tooth when I was 14 which did deteriorate some of the bone. (I saw a dentist every sixth months, my dentist somehow just didn’t catch it even after I complained 5 years before.) Anyway from what I know my grandpa has the same problem of not getting numb and was told it was just his nerve structuring. Red hair does run in my family (my hair is brown though) and so does lack of teeth enamel. A couple of ears ago I got into a car accident and was pumped with morphine and anesthetic so that they could put a tube through my chest and to the doctor’s disbelief I felt all of it. Anyway, with my last dentist he gave me the anesthetic with adrenaline after I jumped in the chair and after about 15 shots in total I still had pain. I get completely numb but it seems that when they get closer to the nerve I get a sudden unexpected jolt of pain which literally causes me to jump. Their reasoning was to prescribe me an anti anxiety medication, but it doesn’t work on me and nor noes morphine or laughing gas in normal amounts. I’ve had them from injections in the er about 3 times and they just don’t work. Anyway, I’m about to go to the dentist again soon after about a year. I just recently switched to a better dentist but unfortunately she takes HOURS, but my mom’s insurance just isn’t that great so we can’t be choosy. I just don’t know what to do. I have 6 cavities and 5 crowns to get done. when they told me that I literally almost passed out, I went extremely shaky and pale and started crying in a full blown anxiety attack. My problem isn’t the pain, it’s that I don’t know when it will come so as a reflex it causes me to jump hard in the chair, and I been yelled at multiple times for it and dentists saying they almost cut my tongue off. So I’m just afraid what will happen when I jump from the sudden random pain and will get a serious injury. I can’t afford to be put out because my insurance won’t cover it so I’m just looking for a solution. If I ask her to give me like 25 shots and numb every single area possible will that prevent it? I’m desperate because I fear that they next time I jump it’ll be my face or tongue cut off.

  12. Victor Stephens says:

    I had a right back molar extracted yesterday. It was the most horrific and agonizing dental experience of my lifetime. Things began well as I was very relaxed from the “laughing gas” and the right side of my face was numb. However, after the dentist began extracting the tooth, it was like the cloud I was relaxing on, ran into a brick wall. The pain was excruciating as the extraction procedure lasted for about 10 to 15 minutes. Additional injections of Lidocaine failed to reduce the intense pain.

    This was the second time I had a tooth extracted while awake. The first extraction was a breeze … feeling only slight pressure and no pain. So, I was caught off guard when the second extraction was not pain free as the first extraction. If I ever have another tooth extracted, I will option to be put to sleep.

  13. I went to get a molar removed a few days ago, the dentist had to inject me atleast 20 times and i still felt extreme pain as she started and jumped out of my seat, we couldnt get me numb and she referred me to an oral surgeon.. my appt is monday and im scared to death ill have to go thru that pain again….how do i get this tooth out. Help! Ty shannon

  14. Elaina Scott Knaus says:

    I had 2 lower molars filled and one upper at the same time. It usually takes 3 rounds to numb me. After I left my jaw was very sensitive. I have had root canals and orthodontic work on my teeth before so the time my mouth was open for procedure was no biggie for me. Now 2 weeks after my jaw is still compromised, I cannot bite into food, I am not able to open very wide, and my neck is stiff opposite from the side that had work done. I went back and had them adjust my bite once which was difficult since I can’t open wide. I can’t pull my lower jaw teeth in front of my upper teeth, and when I try my ears feel weird. I went to Walmart and got a bite guard to help with my urge to clinch at night, but am having to wear it all day now to help ease my jaw.

  15. Hi Dr. Calcaterra,

    I came in contact with your blog and it is wonderful. I have a had a chronic dental pain problem that has stumped dentists and specialists over the last 9 years. I wont go into the details, but I have a had many, many injections for evaluations and dental work. I went to an alternative health web site that was making proclamations that dental anesthetics are possibly dangerous long term since they contain coal tar type substances(that may be carcinogenic) that are not broken down in the body very well. Certain anesthetics such as Lidocaine and Carbocaine. Others like Septocaine are less dangerous. It has me a bit worried, but not being a scientist or dentist as well as reading and interpreting data I probably have no clue on what I read. I certainly have more dental evals and work ahead of me. Thank you for your time and this wonderful blog you provide.


  16. christina says:

    I don’t know if you have come across this in your practice, but I have a condition called Ehlers-Danlos Syndrome. Long story short, its a connective tissue disorder that makes it EXTREMELY difficult for us to get numb. Case in point, I needed a root canal on a lower molar last night. My dentist and I have a long relationship, and he understands my condition and what it takes to get me numb. SIX shots of novacane and a nerve block later, I STILL wasn’t numb. AT ALL. It was a night mare. He couldn’t do anything. Part of the reasoning behind it is that with EDS we have what are called “flares” which makes all of our joints, tendons, connective structures inflamed. And it sucks lol. Also “double jointed” people are people with a type of EDS. Its the one I have 🙂

  17. Anita Parfitt says:

    Dear Nicholas, I got an infection in my bottom left hand molar back in August while on holiday. Early September when I returned I went to see my dentist, he agreed it was an infection so antibiotics was prescribed with a follow up appt for a root canal. At this next visit 6 injections and I was only partially numb, he was able to open the tooth & start the root canal but couldn’t finish it. One more visit 6 more injections and still could not numb or finish the job, temporary filling back in but this time the next day the tooth cracked in half!! He was able to glue it together twice more The next visit he injected my mouth another 4 times & then called another dentist in to do a block right in the back of my jaw. Everywhere was numb except the same corner of my tooth!! He did an imprint for a crown & filled it temporarily again which fell out that night. I went back and a lady dentist did another temporary filling which stayed until my next visit. On Thursday he used a wand to inject straight into the canals (painful) the one canal as usual did not numb so couldn’t be done. He fitted the crown temporarily, since then I have been in pain. The crown feels high & im taking painkillers again, it feels like there is another infection.
    Although I have dyed blonde hair I am naturally an auburn Irish woman. I am now taking blood pressure tablets since December. So I’d like to ask if you have any suggestions please. Thank you

    • Anita,

      What you’re describing happens occasionally. It is really a perfect storm: a lower molar with a history of infection who may be a redhead.

      It sounds like most techniques have been tried and exhausted on you.

      There are some techniques where a very small hole can be drilled into the jawbone allowing local anesthetic to be deposited next to the tooth. I don’t know if that is available in the U.K. Other techniques involve sedation. Between the two, the procedure can likely be accomplished. Hope this helps.

  18. Michael Nielsen says:

    Any recommendations, since I was a child, I have suffered through ineffective local anesthetics, followed by a couple of rubber blocks jammed down my jaw, to prevent me from closing my mouth, then held down, while the dentist just drilled, completely ignoring my pain, claiming that i was just me being hysterical, as the local has taken all pain.

    As an adult, I now have a really significant anxiety towards dentists (and doctors, they are the only two thing, that I’m afraid of – almost literally). I have been searching for dentists (or even research), that accepts that there may be issues with the local, and perhaps are open, or aware of other means of performing the local, those dentists are, however, extremely rare here.

    Once while I was a child, I got the injection AND NO (Laughing gas), and the tooth extraction was almost painless, and another dentists has successfully, used a strange device, that “clicked”, hitting nerve points in the mouth (10-15 times), however in about 41 years, these two are the only pain-free procedures that I have tried. (I haven’t got a clue what that clicking device was, but it worked, but no other dentists uses it, and the one that did, has gone on pension).

    Sometimes dentists have tried up to 6 x the normal dose of local, however, I still feel the pain acutely, and two days ago I was made aware that people that have red hair, or tendencies that way, have a heighten resistance to the locals, and combining this with anxiety, I’m near impossible to numb..

    Are there any alternatives to the usual needle, or do you have an idea of what the name of that click device that the other dentist used was ?

    • Michael,

      You are 100% correct about redheads having a resistance to local anesthesia. I’ve blogged about that here: http://directionsindentistry.net/redheads-feel-more-dental-pain/

      The research clearly suggests that anxiety decreases the pain threshold and makes you more likely to feel pain.

      The “click” device to which you refer – there are different ones out there. Nearly all purport to penetrate bone and allow the local anesthetic to literally surround the tooth. The devices are effective, but they can be expensive, difficult to use, and sometimes the healing afterwards can be lengthy.

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