What is SIgA?
IgA is a type of antibody that protects against infections of the mucous membranes lining the mouth, airways, and digestive tract… it is your first line of defense on the mucosal lining and it makes up a majority of your entire immune system.
Some people have a genetic deficiency and present with low levels of SIgA and frequent infections. Others acquire a low level after their intestinal tract becomes over-run with abnormal microbes.
SIgA helps to shape the composition of the microbes in your gut!
Extraordinary amounts of immunoglobulin A (IgA) are produced in your intestinal mucosa daily, it is known as SIgA and is secreted into the human gastrointestinal tract. SIgA production is driven largely in response to mucosal antigens (bugs or food) encountered by gut-associated lymphoid tissue (GALT). It is clear that secretory antibodies are directed against at least two broad classes of antigens. The first is associated with enteric pathogens (the “bad guys” or infections) and their virulence factors, or things that the bugs secrete, like toxins.
The second broad class of antigens recognized by SIgA is associated with the intestinal microbes or commensal microflora (the “good” guys, like probiotics). In experimental animal models commensal bacteria are potent inducers of secretory antibodies; in humans, it is estimated that between 25 and 75% of intestinal bacteria are coated with SIgA. This could explain why one of the most basic ways to improve levels of SIgA is to give a patient probiotics and saccromyces boulardii.
There is also evidence from mice that secretory antibodies play an important role in shaping the composition of the intestinal microbiota, which in turn can influence your gut’s defense against invaders and enhance resistance to the intestinal infections.
Profound Role in Intestinal Balance and Your Health
So because SIgA can neutralize the “bad guys” and shape the “good guys” SIgA plays a profound role in intestinal balance and health. SIgA is the main immunoglobulin in mucus secretions. The intestinal cells produce about 2-3grams of SIgA every day! And production tends to peak in childhood and start to decline after about sixty years old.
This is our first-line defense against gut pathogens like bacteria, food proteins, parasites, fungi, toxins and viruses. SIgA antibodies prevent micro-organisms, food proteins and cancer-causing substances from binding to the surface of absorptive cells. Effectively, they attach themselves to invading bugs and trap them in mucus to prevent them from going anywhere!
The antibodies also ‘tag’ foods as acceptable to the body and this suggests why low SIgA levels can be a factor in developing and progressive food allergy and intolerance. Intestinal permeability is also related since, if levels are low, repair of mucosal tissues can be compromised. This is often referred to as Leaky Gut and can coexsist with low levels of SIgA.
Certain SIgA antibodies have been shown to directly quench bacterial virulence, whereas others help with uptake of SIgA–immune complexes by mucosal dendritic cells and result in down regulation of pro-inflammatory responses normally associated with pathogens and allergic antigens.
In fact it is becoming increasingly evident that human health is inextricably linked to the gut microbiota, intestinal homeostasis, and mucosal immunity. IgA is at the centre of this dynamic.
Testing your SIgA
Secretory IgA is quite independent of blood IgA levels so just because one is normal, doesn’t mean the other is. SIgA can be measured in different ways, including stool and saliva. Levels can turn out to be low or high. Stool measurements have traditionally been based on sample extractions from animal models – it is hard to ask a mouse to spit! Salivary samples provide a systemic overview of circulating SIgA.
Ongoing low levels can help to explain why people can’t shift an immune problem like allergies, chronic skin conditions or infections. It can also explain why they find it hard to get rid of a microbial infection, too. Celiacs and those with IBD can have low levels and chronic stress has a major effect on SIgA levels. Certain medications can lower levels – including anti-inflammatories. Other factors includeviral infections (like Epstein Barr viruses), poor nutritional status, food allergies, ongoing stress. Interestingly some studies have shown variations in levels with gender and age – male patients often have lower levels.
* These statements have not been evaluated by the Food and Drug Administration. The product mentioned in this article are not intended to diagnose, treat, cure, or prevent any disease. The information in this article is not intended to replace any recommendations or relationship with your physician. Please review references sited at end of article for scientific support of any claims made.
If someone has low SIgA, what should they do?
It’s important to find out why the SIgA is low and treat the root cause. I suggest finding a functional medicine doc in your area who does comprehensive digestive stool analysis. Often if the gut microbiome is imbalanced or there is an infection it will lower the SIgA. Other people are born with genetic deficiencies of IgA. Probiotics are helpful but treating the cause is essential.
What if SIgA is above normal? Mine is 76.149 on a range of 10.0-60.0 ug/ml (done by saliva test).
High can indicate a chronic infection, like parasite or yeast. I suggest finding a functional medicine doctor to test the stool for infections and treat to balance your gut microbes.
Thanks for replying! I do have an upcoming doctor appt.
My secretory IgA was recently tested via stool sample and came back as 10.6mg/dL and the reference range was listed as 54-204mg/dL. My doctor said that it was okay that it was low because that means there is no chronic infection; however, I have digestive issues and possible food sensitivities. I just want to be sure I understand this correctly. To me it seems that my IgA is low and could be a contributing factor to some of my current issues. Can you offer any insight?
Hi Lauren, low sIgA usually means some chronic infection or dysbiosis or a stressed gut (food allergies, celiac disease, etc) Probiotics, saccromyces boulardii, and IgG or whey protein (if you are not sensitive to diary) may help.
Very helpful! My ND was good at telling me what my low number meant, but seeing the explanation written out is very helpful at solidying the information for me. Thanks for the post!
As a survivor of Stevens Johnson Syndrome, my health is beyond vulnerable. For over three years, I have followed a tight regime, isolating many irritants. My system considers most normal things toxic, responds intensely not limited to anaphylaxis. Being in the proximity of paprika, curry, peppers, cooked garlic/tomatoes, etc will cause violent anaphylaxis. Medications, supplements, foods, topicals, etc… all are huge problems. I am currently recovering from a SJS relapse caused by Xymogen ProbioMax Daily DF. I really was hoping to progress in healing yet have set myself back significantly. So, the solutions you mention are all unavailable to me. (Have not tried isolate saccromyces boulardii but don’t see why I wouldn’t react to that also.) Hoping you have some other insights. Desperate. (My mucus membranes have been destroyed; SJS burned me internally then externally.)
If you are not already doing, I suggest following a 100% organic, GMO-free, unprocessed paleo-autoimmune protocol to begin healing the gut/mucosa and immune system. You may also want to consider SLIT therapy to desensitize your immune system. Glutamine powder is helpful for rebuilding mucosal surfaces but as you already know use extreme caution with probiotics.
Glutamine powder is helpful for rebuilding mucosal surfaces but as you already know use extreme caution with probiotics.
I couldnot understand this sentence. why should i use probiotics with caution? should not be taken along with glutamine? Kindly please explain.
You may take glutamine and probiotics together
This November, it will be four years detoxing from the offending drug that caused Stevens Johnson Syndrome. This trauma severely damages the mucus membranes; this is why I am interested in measuring SIgA. I have been following a tight nutritional regime for three years, not a deviation for over two. This recent relapse has me committed to bone broth again. My immunoglobulins are off; the more I learn I believe there is an amino acid imbalance too. How is saccromyces boulardii different from other probiotics in healing the gut? and is it dairy at the base? Much gratitude.
Saccromyces boulardii is a probiotic yeast. Most are not dairy based and work well but should not be used in someone who is sensitive or allergic to yeast.
Thank you; I react to yeast.
I found out i have low SIgA. Testing was done maybe 5 years ago.
My chiro assume its’ still low…
Leaky gut, adrenal fatigue, lots of genetic mutations (COMT, MTHFR)
hashimotos (controlled with GF and anti inflammatory diet)
possible mold exposure…
yes, could be any of these things… test don’t guess
my chiro put me on Saccromyces boulardi, if i have candid should i not be on this pro?
Saccro B is fine for fungal dysbiosis
Hi Dr Jill!
Loved the write up!
I just found out that I have very low levels of SIgA (My level is <0.1 when the normal level is supposed to be 51-204 mg/dL). I live outside of the US and in a part of the world where functional medicine practitioners are non-existent. I'm hoping to schedule a consult with a practitioner in the US sometime next year but am wondering what I can do to support myself in the meantime.
I've suffered from chronic skin conditions for about 10 years now and my diagnosis has not been confirmed but it's a possible overlap of eczema, psoriasis and pemphigus foliaceus (or so says the dermatologist). I also have multiple food intolerances (IgG mediated).
My hair mineral analysis showed high levels of mercury, aluminum, barium and antimony and low levels of molybdenum. I also have low levels of vitamin C.
I'm kind of stuck. Avoiding my trigger foods used to put me in remission but even that doesn't seem to help anymore. Like I said, I'm hoping to secure a consult with a functional medicine practitioner next year but am looking for ways to prevent further deterioration in the meantime.
Yes, likely all of your conditions are related. The very first thing I would do is avoid gluten 100% in your diet. Second I recommend testing for dysbiosis with stool testing and breath testing for SIBO – then treat any infections that you may find.
Thank you Dr Jill!
I’ve been gluten free for several months now and my diet is almost 100% AIP compliant (the only exception being organic brown-rice which I seem to be okay with). I’ve also done stool tests which show no dysbiotic flora and fair amounts of beneficial flora. I haven’t done the breath test though so maybe that should be my next course of action. If an infection is found can it be treated using regular antibiotics (by a normal physician) or would a functional medicine practitioner treat it differently?
Just came across this study today Immunoglobulin A deficiency in Celiac Disease in the United States
Hi Jill, Thank you for your article. I am wondering what you know of rectal ozone insufflation? My stool test showed SIgA at 22 (in a 400-800 range) I have dealt with chronic anal fissures that are triggered by too much fruit, sugars or alcohol, or sometimes just seems out of the blue. I have never been constipated so it is not a local trauma issue. I have tested for blastocystis h. and followed the Paleo diet with all sorts of herbs and probiotics with not much improvement. I am now taking s. boulardii and seeing such positives from it in regards to the quality of my stool. Do you think the rectal ozone will help the healing of the mucosal tissue (or be too irritating) while helping the body to irradicate any pathogen that might be the underlying cause? Thank you!
I don’t recommend rectal ozone
Will it destroy the beneficial bacteria? Is that why you do not recommend it? Thank you.
I have a severe low SigA. and I have a stomach cramps and bloating and also unstable stool.
are they related to low siga? because my colonoscopy test result was normal. every thing was normal except low siga. What may cause low siga?
Low IgA may be a consequence of dysbiosis rather than a cause….
Hi Dr. Carnahan,
Do you recommend stool testing of secretory IgA or saliva testing? Is one better than the other? Also, can you recommend some specific labs that provide kits for both saliva as well as stool testing?
I’m getting ready to do a baseline test then see if I get some improvement in the sIgA levels after taking anti-microbial herbs. So an easy-to-do before and after test (that is reliable) would be great!
I recommend serum IgA and stool secretory IgA. I do not rely on salivary testing.
Hi Dr. Jill,
Thank you for this answer! Can you recommend some specific labs with kits for the stool secretory IgA?
If I get a couple of names, my physician said she would set up an account and get me a kit.
Hi Lynn – Genova Diagnostics and Doctor’s Data are both good companies to use
Thank you so much for helping patients via these emails! I appreciate the caring that goes into that.
I can’t thank you enough for this informative article!! I mentioned it this morning on the Facebook SOLVE ME/CFS Initiative site. I’ve had severe ME/CFS for 14 years and have done so many protocols and taken so many supplements, but still am disabled. As you know, no one has any idea YET what the cause is, let alone a ‘cure’. I still subscribe to the theory that I have to keep addressing anything ‘underlying’ in this 62 year old body! Recently I decided to ‘go back to the beginning’ and see what I missed (as well as the doctors) and realized that in 2003 my SIgA was highly elevated, but by 2007 it was virtually non-existent, a score of 11 with a reference of 400-800 (Diagnos-Techs Expanded GI Panel). So your article reassured me that it’s not likely the cause is genetic. I realize that no one addressed the SIgA, only the yeast, Blastocytis Hominus and a myriad of overgrowth of bacteria. We did completely eradicate the B.H. with Oil of Oregano and got the yeast candida completely under control, although it took about 2 years and a dozen different targeted protocols. I don’t have any food allergies and no pronounced food sensitivities (been tested numerous times) and tested negative twice for Celiac, which is a positive. I think however, I’m going to add the Saccharomyces Boularii and Glutamine Powder to my regimen before I spend the money once again for all the G.I. Tests. Thanks again.
Which brand would you recommend?
Would you take probiotics as well and which brand as well? I have candida so would I treat that first then add it these?
I prefer Xymogen ProbioMax daily DF 1 daily or Klaire Labs Ther-biotic Complete. You can order from Xymogen directly using code: DrJill and last name Carnahan.
I have a low secretory IGA of 14.2. I have had constipation since I was 5 with recurrent body aches and headaches. Recently I have been trying to eliminate constipation since there is so much more info available these days!. I was tested to have blastohominus, strep and candida, and hashimotos. I have already been eliminating gluten and sugars and dairy for some time. Recommended treatment is a mainly meat/veggie diet for 10 weeks with a parasite cleanse. Low carb diets can worsen Hashi motos and I did have an exacerbation from this in the past. Also eating has become a full time job for me to maintain weight with these restrictions despite healthy fats. Will it be harder to fight parasites with low IgA? Is the low carb diet necessary to Eliminate these issues? I worried about creating more harm than good…Please let me know your opinion. Thanks!
Hi Candice, I suggest trying to find the root cause of your constipation and treating that…. candida, SIBO, or hypothyroid are all possible causes.
Hi, I did a comprehensive stool test and the results showed dysbiosis and candida overgrowth. Other tests showed that my secretory IgA levels are extremely low. Can dysbiosis/candida lower our secretory IgA? I have leaky gut and multiple food sensitivities.
Hi Leonardo – short answer is yes!
Hi Dr. Jill,
I have elevated SigA, determined via a saliva test. I am treating SIBO and Candida, and have also been diagnosed with Hashimoto’s. It sounds as if both elevated SigA and low SigA mean kind of the same thing? I’m kind of confused about it and what should I be doing to address it. Is it just something that should normalize as I bring my body into a better balance? Thank you!
Are you aware of any studies that compare SigA before and after taking immunoglobulins, as well and determining if it improves oral tolerance? I am unable to locate actual studies.
Hi Mandy – you can search PubMed for studies. I do believe there are some small studies using Serum derived bovine immune-globulin
I would love to find some real time testimonials by people who were able to improve sigA levels. I’ve been searching the internet for years. My sigA has been low since 2017 and have worked with numerous naturopath. Faithfully following struck protocols and battle one illness after another. H Pylori, canidida, SIBO, many pathogens and parasites and still fighting H pylori and taking S boulardii, colostrum vit A, and specific herbs and probiotics. No successful testimonials be found on the internet.
Thanks for this excellent article. I recently had mine show up as 4 when the low range for the stool test is in the 500’s. This may explain my chronic childhood illnesses and ongoing digestive issues. What is the genetic SNP for low SIgA?
I don’t know a specific SNP for low sIgA in stool. There may be one for selective IgA deficiency which is diagnosed by low serum levels of IgA
Can slgA go down quickly after a violent episode of vomiting, and not eating well for a few weeks due to the recovery? I have never had digestive issues but in July had a severe stomach something that caused a lot of vomiting. Afterward I “tanked” and was so tired I ran an EBV reactivation test and DID test positive for that. Because I have never had food/digestive issues I wonder if this could have suddenly came about? My levels came back “sub 5” on the Data test. Thank you for this informative post.
SIgA can respond to infectious triggers and go up or down
Can a person be born with a low IGA?
Hi Jennifer – yes, selective IgA deficiency tends to be a life-long diagnosis
I forgot leave this comment, no one in the family has low IGA just my mother.
She started having problems at teens developing infections, her health fell down in her mid 40s now dealing really hard time right now she’s 56.
She a person be born with low IGA?
Hi, just had a sIgA score of 64 µg/g with a range of 100-1200 µg/g from a lab in Germany stool test. Is that a fairly low score or not to bad
Your sIgA is low and I recommend supportive measures such as bovine immune globulins and saccharomyces boulardii
Hello. I’m Kelly 21 years old. I suffered from low secretory iga since i was 9 years old and never felt good after that. The only way i feel better is using antibiotics. I also have a swelling in my abdomen. I can’t do anything anymore. I take 8 tramadols a day to manage the pain. But also that is not a lot of help.
My siga was beneath 167 , they couldn’t measure it accurately, but it had to be between (510-2040).
Every doctor is saying i have a lot of stress and put me on antidepressants. That’s when my pain started getting worse too. I also last 8 kilo’s in 2 weeks. That’s when my hormones started shutting off. But nobody wants to help me or listen to me
I really want to get better. I tried everything. From a fodmap diet, to antimicrobial therapy, parasitic drugs, probiotics, glutamine, also Standard medications for IBS. But i don’t even get cramps or any of the typical symptoms of IBS. Can you please give me some advice.
I also have an allergy for horses where i’m always exposed too , every day for a couple of hours.
I am so sorry to hear how you have been suffering… With low secretory IgA you may have underlying gluten intolerance or or intestinal permeability caused by severe dysbiotic. If antibiotics helped in past, I suggest getting tested for lyme disease and co-infections like babesia or bartonella as these can cause significant pain and autonomic dysfunction contributing to symptoms as well. You can find a functional medicine trained doctor in your area and get additional testing to find root cause.
Nobody in my area really can help me, i went to everyone. Nobody knows what secretory iga is.
Can you give me some suggestions in how to increase it ?