Herx Reaction vs. Allergic Reaction

This can be a confusing topic among Lyme patients. Sometimes it can cause serious concerns and leaves you to wonder if you are experiencing a normal herx reaction, or if you are indeed having an allergic reaction to your antibiotics. I figured I would share some information that would bring this to light for you.

I would consider this a two-parter, to my original post, “The Herx Reaction”. Want to read the first part? You know you do! My first post was written to share with you what a herx reaction is, and some of the basics about this phenomenon. Here is the link for you to read: https://kimmiecakeskickslyme.wordpress.com/2013/09/16/the-herx-reaction/Β  πŸ™‚

A herx reaction is often misdiagnosed as a drug allergy. Strong disease symptoms within patients can be difficult for doctors to decide what is a herx or a drug allergy, especially in non-Lyme literate doctors.

Another thing to understand about herx reactions is that it does not mean disease progression. It can create new symptoms, or bring back previous symptoms. Just because you feel worse, does not mean you are actually getting worse. Make sense?

Herxes are uncomfortable. They are NOT fun. But perhaps an inevitable part of the healing process. Science suggests that having these reactions means that the antibiotics are indeed doing their job.

The importance in this is knowing if you are having a herx reaction, versus having an allergic reaction, and knowing there is a balance when you are having herx reactions as they can become quite severe.

So, how do you know if you are having a herx reaction or having an allergic reaction?

There are many symptoms to having a herx reaction. Some of these symptoms include:Β 

-joint and muscle pain

-increased fatigue, exhaustion

– sleep disturbances


-muscle cramps

-chest pain

– chills

– nausea


-flu-like symptoms

– throat swelling

– lymph swelling


– low grade fevers

-facial palsy

-IBS symptoms

-conjunctivitis (on a side note, this is Lyme conjunctivitis, and is not contagious.)

-hypertension or hypotension


– skin rashes

-headaches and migraines

-irritability, rage, confusion, and brain fog

-uncoordinated movement

You are most likely to have an allergic reaction to medications if you have asthma, high blood pressure, or heart disease. Some signs of having an allergic reaction to your antibiotics include:Β 



-skin rash

-facial swelling


-shortness of breath




In severe cases of an allergic reaction, anaphylaxis can occur. Anaphylaxis usually begins within minutes of exposure. Some of the symptoms of anaphylaxis is tightening of airways, shock, a weak rapid pulse, nausea, severe vomiting, severe diarrhea, and dizziness. IF YOU HAVE ANY SIGNS OF ANAPHYLAXIS WHEN BEGINNING A NEW MEDICATION, SEEK IMMEDIATE MEDICAL HELP!Β 

On a side note, if you are going to be taking new medications on a frequent basis, I highly recommend suggesting to your doctor getting a prescription for an EPI pen. Hopefully, no one will ever have to use one, but in severe allergic reactions, it just may save your life.

Two effects of having an allergic reaction that might not be immediate, but rather longer term, within a week or more exposure include drug-induced anemia, which destroys your blood cells, and serum sickness. Serum sickness can cause rashes and joint pain, and can also damage your organs. This can also be confusing as it isn’t onset, with rashes and joint pain, but it shows that it is important to frequently get bloodwork done to make sure everything is okay.

As you saw listed there, some symptoms might very well be confused with having an allergic reaction. The three main confusing symptoms are as follows:

Tachycardia is probably one of the biggest worries as to if you are having an allergic reaction. Many people with chronic Lyme or co-infections, particularly Babesia, tend to have this issue, and it does not necessarily mean you are having an allergic reaction. It is a scary feeling if you are having rapid heart rates, so please contact your doctor in order to be on the safe side, especially if you have not faced tachycardia issues in the past.

Pruritus, or an itchy feeling of the skin, can also be perceived as having an allergic reaction. There can actually be many reasons for this feeling, whether it is a neurological issue, or a vitamin deficiency, so it might not even be related to a herx!

Throat swelling can be a terrifying thing. Once again, this can be a herx reaction, as your body might be having a hard time eliminating toxins from your body. From personal experience, when I first started treatment, I was having a hard time starting out on my antibiotics. After about a month, it was Halloween of 2012. You know what that means: candy. I was already completely loaded with toxins in my body, and I had a little kit kat bar. I was literally gasping for air. It scared the living bejesus out of me. Because I could not eliminate the toxins from my body, I was completely overloaded eating a big “no no” food. Once I discovered that I had a MTHFR genetic deficiency, and addressed it, it made my world of herx reactions much easier. After all that blabbering, it generally would mean that you are completely overloaded with toxins, causing your herx, and adding other elements can make your symptoms much worse.

Skin rashes can be confusing as they can show that you are having an allergic reaction. If you quickly develop hives, you are having an allergic reaction. Here is a picture of what hives looks like if you are not aware:


Skin rashes can also be produced by having a herx reaction. They can come in many different appearances and forms. A picture of a herx rash is:

Using myself as an example, I have ACA, a skin condition known as “Herxheimer disease”. Here is a picture of one of my tootsies when I am having an ACA flareup:


On a side note, if you develop a rash over time, it may not be a herx reaction or an allergic reaction. Another fun skin condition that I have, that kind of holds the appearance of hives, is called tinea versicolor. It is caused by yeast overgrowth. Yeast issues are very common among long term antibiotic users. Here is a picture of what tinea versicolor looks like:


Is there any other ways to tell herx reaction vs. allergic reaction? Why yes, there is!

Timing can help you determine if you are having a herx reaction or an allergic reaction. As I had mentioned, one of the ways to know you are having an allergic reaction is that it is often a sudden onset. A rash should appear quickly, and reactions generally subside after a few hours. It should be noted, however, that having a reaction like an intolerance can build over time.

There are many beliefs as to the onset of having a herx reaction. Some researchers believe that a herx reaction can occur within a few hours of taking an antibiotic, or up to 10 days after starting an antibiotic. Some believe between day 3 and day 5. Some believe between 4 and 24 hours. Some say that herx reactions can last for weeks. I say potatoes, you say poh-tah-toes. Lyme and confections clearly need more attention and research. But I am sure you already knew that. πŸ˜‰

Blood tests can be a tool to use in order to tell if you are having a herx reaction or an allergic reaction. Ways to tell you are having a herx reaction can show up in your bloodwork. Your white blood cell count can elevate, as well as your creatine levels. If you are not sure if you are having an allergic reaction, one of the blood tests that you should follow is EOS. If your levels are at 30% or higher, it is a high indication that you are having an allergic reaction.

It can be extremely difficult with those that are very symptomatic to try to decipher the two. If you have established that it is indeed a herx reaction, it is important to remember that you should never have to deal with extreme herxes. If you are, then you are in fact being counterproductive, as the toxins are not getting out of your body fast enough, and your body will not be able to make full use of the antibiotics to fight the bacteria.

Some things you can do if you are suffering from severe herxes are adjusting your dosages, embracing the many ways to detox (which will in turn ease your herx symptoms), and stopping altogether and taking a break. This can be overwhelmingly upsetting, but if your body is severely debilitated, your treatment isn’t going to work. Don’t get discouraged if your doctor suggests a break. It will give your body a chance to clear itself out before you fight again.

I hope my research helped everyone out! It can be a scary thing trying to tell what is normal, and what isn’t. If you are new to the Lyme battle, you should know that the journey can be long, uncomfortable, and painful, but in the end it will be worth every bit of it to gain your health back and put this disease into remission. If you have any doubts or are facing serious and concerning issues, contact your doctor and seek medical help immediately.

http://www.affairsofliving.com/imported-20100106014405/2010/7/5/helpful-hints-for-battling-a-herxheimer-reaction-or-my-adven.html, biovedawellnes.com, http://www.mayoclinic.com, lyme101.wordpress.com, wikipedia.com,http://livewithcfs.blogspot.com/2011/10/managing-herx-reaction.html,chronicillnessrecover.org/index.php?option=com_content&view=article&id=16, top picture source: hradvocacy.org.uk

21 thoughts on “Herx Reaction vs. Allergic Reaction

  1. Thank you, Thank You, Thank you, Kim! I have had all of the above and felt very confused about the herx vs allergic reactions I was having. Magnesium brings on tremendous joint pain for me, for example. If I take just one supplement, excruciating joint pain will last a couple of days, and sometimes I am bedridden from it. I never knew why this happened, but I’m thinking it is a herx reaction, according to the information you’ve provided here. When I’ve had penicillins, I’m down and bedridden with joint and muscle pain for three to six months at a time. I’m thinking this might be a herx, not an allergy, but nonetheless, it is so extreme, my medical information lists it as an allergy. As you point out, if your body is not effectively eliminating the toxins, the herx reactions can be very unhealthy, counterproductive, and even dangerous. I’m also glad to know that bloodwork can help identify a herx vs allergic reaction. I never knew that. I always look forward to your posts. Thanks for all the great info!

  2. thanks, I take it it’s safe to continue with antibiotics after Herx reaction has subsided. Could have been this that I got after my last antibiotic treatment, so not limiting the options next time. Pretty scary seeing the rash progress everywhere on skin, only stopping to the neck level (brain-blood barrier possibly working here)

  3. Pingback: Herx Reaction vs. Allergic Reaction | Slices Of Lyme Pie

  4. Hi, a few years ago I used creatine. Started vomiting for a long time until there was nothing left to vomit. then I started getting the rash afterwards. I felt like I was about to pass out. my ma rushed me to the hospital and got there just in time. Heart rate dropped to 20 and went lower and went into shock. I saw some stuff that I dont know if it was real or not but they treated me immediately and started getting better. knocked out a hour after this and woke up the next morning with no rash or anything. Im from South Africa so I know they saved my life but they took 2 sepperate samples of my blood but they still didnt know what was wrong. Even tested what I was allergic to a year affter this and they still cant find anything. Now im allergic to milk products from the day I was born and I found out that it creatine is high in milk. But I had no energy. for months!!! when i walk to the front gate to pick something up and back I was out of breath. This went on for at least a year. Slowly getting back to normal. But I lost all my muscle. lost 15 kg. Im a skinny guy again!!! After working so hard. Now that I have energy again I wanna start gyming but Im afraid of what to take. Is there even anything I should try or should I just completely stay away from any kind of supplement? Or should I get a epipen and just try something. Like pre workouts and stuff like that. even though I also dont know what in those kind of stuff

    • I would maybe see a naturopath and tell them what happened and they could suggest something? Or very carefully read to make sure there isn’t any ingredients you know you may have an issue with.

  5. Pingback: My First Herx – Miss Diagnoses

  6. Wow. Kimmoe, your post is very informative.
    Thank you! Right now I am confused and I am
    Hoping you can help me. I have been taking Clindomyacin and Plaquenil for the last 10 days to treat Babesia and came home yesterday after playing basketball in the sun and realized I had a horrible rash all over my chest, stomach, neck, and back. After taking Benadryl it didn’t go away at all and looked to have gotten worst. I went to urgent care today because my LLMD is unavailable during this three day weekend and the PA had no idea what was going on – thought contact dermatitis. So, I took 40mg of prednisone in the hope it would die down. It’s been less than 12 hrs, but no luck yet. He said I could resume taking Clindomyacin and Plaquenil, because he didn’t think I was having an allergic rxn, but I am hesitant to do so if I am having a major herx or an allergic reaction. Any insight you may have is greatly appreciated. It seems they will not allow me to post photos, so if there is another way to show them to you I’d be happy to send via email. How long did it take your rash to go away? Thank you! Kaitlyn

  7. Im no professional, but I feel you just made an excellent point. You obviously know what youre talking about, and I can truly get behind that. Thanks for staying so upfront and so truthful.

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