Dear Mark: Omega-3s and Fish Allergies

Omega 3 Fish OilsBy now we all know the benefits of fish oil and its omega-3s: lower risk of heart disease, stroke and cancer, less systemic inflammation, lower risk for depression, better skin, and so on. Although fish and fish oil supplements are the best sources for these omega-3 benefits, there are nonetheless scenarios that rule out these sources.

Dear Mark:

I’m sold on the benefits of a Fish Oil Supplement and I’m interested to start taking one. However, I have had serious allergic reactions to Shell Fish in the past, and an allergist has shown me to be reactive to most fish in general. As such I have avoided anything and everything that swims for a very long time. Maybe it’s possible my allergies were due to inflammation caused by my CW diet, but I’m still wary to test my theory now that I’m eating Primal. I feel like I’m missing out on a huge variety of food and supplement options. Question: I know anything can cause an allergic reaction, but is there any scientific basis for Fish Oil Supplements causing allergic reactions in people who have demonstrated allergies to fish/shellfish? And if so, what are my options for proper Omega-3 supplementation?

Thanks to DJK for this week’s question. First, let me expand on the allergy subject. Fish allergies are most commonly set off by fish proteins and less commonly by fish bones and skin (found in gelatin products). Even if you’ve shown a sensitivity to finned fish, you don’t need to rule out fish oil just yet. Although processing varies considerably between brands, true purified fish oil shouldn’t contain anything that would incite an allergic reaction. For those with a sensitivity but not full-blown allergy to fish, I’d recommend giving a high quality purified supplement a careful but fair try. A very small study showed that purified fish oil supplements were safe for those with fish sensitivities.

If, on the other hand, you’re one of the few with a serious, life-threatening allergy to fish I’d recommend a different omega-3 route. Your best bet is to come at it from multiple angles.

  • Decrease omega-6 intake and inflammation inciters in your diet. Although omega-3s are essential in their own right, they’re also needed to balance out the high levels of omega-6 in our modern diets. A clean Primal Blueprint diet free of processed foods, grains and omega-6 based oils will cut go a long way to reducing the numbers needed to maintain the golden 1:1 omega ratio.
  • Eat grass-finished and wild game meats (especially organ meats). Both offer a much better omega ratio (1.6:1) than factory farmed meats.
  • Increase your ALA omega-3 intake. Although the body’s conversion of ALA to EPA and especially DHA is limited (for men: 8% to EPA and 0-4% to DHA; for premenopausal women: 21% to EPA and 9% to DHA), a good wallop of ALA offers its own benefit and a leg up in the EPA/DHA department. Ground chia and flax seeds are great sources, as are the green purslane and omega-3 enriched eggs.
  • Finally, add a “vegetarian” DHA supplement that is fully derived from algae sources. Health food stores and co-ops are the most likely places to carry them, but plenty of well-known Internet suppliers offer them as well. As with fish oil supplements, look for a trusted brand and refrigerate them to ensure the best quality and freshness.

Thanks for reading everyone, and be sure to weigh in with your thoughts for DJK. As always, thanks for all your great questions and comments, and keep em’ coming!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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64 thoughts on “Dear Mark: Omega-3s and Fish Allergies”

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  1. It’s common knowledge, even for conventional wisdom zealots, that Omega 3’s are essential for proper function and health so this post is most appropriate. What to do if you have a fish allergy? I’ve never really thought about it. Great question and answer. Thanks Mark.

    1. Seal oil! It’s far better than fish oil anyways. Because it’s a mammalian source it’s better suited for our bodies. It also has DPA, similar to what we produce in our breast milk, except our modern diet has depleted that as well.

  2. I’m doing 4000 MG of Fish Oil a day – I’m a noob in the primal diet, and have a history of slightly too high triclycerides in my cholesterol, so I’ll keep that up until it changes.

    I also went a bit overboard on Pumpkin seeds in my first week or two of PD, and for a couple of days felt a bit sick. I’m thinking I might have overdone it…

    I’m all for targeting that 1-1 balance for 6/3 fats.

  3. May want to look into Krill Oil. I get mine from It’s more bio-available, higher anti-oxidant, less perishable than fish oil.

    1. But wouldn’t krill oil cause a reaction for anyone who’s allergic to shellfish since krill is a kind of shellfish? I imagine the purification part would hold for krill oil as much as regular fish oil, but if the main allergy is shellfish I’d be skeptical.

    2. I read about krill oil just after I purchased fish oil. As soon as my Fish oil is gone I am going for krill oil.

  4. Have shell fish allergy. Have taken fish oil for over a year. No problems to date, just better recovery and decreased inflammation.

  5. I’m about to venture into the wild world of supplements for the first time. Currently all I take are Flintstones – cause I love the taste and my wife always has some laying around.

    My thing is that I like seeing measurable results. If I start taking fishoil or other supplements I want to find a way to measure their effect. “Preventing cancer” is good, but not really measurable. Ideas?

    1. not sure about the fish oil “measurement” but Vitamin D is a supplement you can “see” the difference with if you get your Vitamin D serum blood tests done before you start supplementing and then after a couple months of supplementing…

  6. I’ve heard that you need between .5- 1g of epa/dha per 10# of body weight per day. Is this about right? Read it from Robb Wolfe.Can anyone recommend an affordable quality brand.

  7. Some Krill facts for

    Krill oil is made from krill, a small, shrimp-like crustacean that inhabits the cold ocean areas of the world. Despite their small size, krill make up the largest animal biomass on the planet. There are approximately 500 million tons of krill roaming around in northern seas..

    Krill oil, like fish oil, contains omega-3 fats such as eicosapentanoic acid (EPA) and docosahexanoic acid (DHA). However, in fish oil, these omega-3 fats are found in the triglyceride form. In krill oil, they are found in a double chain phospholipid structure. The fats in human cell walls are in the phospholipid form.

    * Over 300 times the antioxidant power of vitamin A and vitamin E
    * Over 47 times the antioxidant power of lutein
    * Over 34 times the antioxidant power of coenzyme Q-10

    The phospholipid structure of the EPA and DHA in krill oil makes them much more absorbable. Krill oil also contains vitamin E, vitamin A, vitamin D and canthaxanthin, which is a potent anti-oxidant.

    The anti-oxidant potency of krill oil is, in terms of ORAC (Oxygen Radical Absorptance Capacity) values, 48 times more potent than fish oil.

    The astaxanthin found in krill oil provides also excellent protection against ultraviolet light and UV-induced skin damage.

    1. I’ve mentioned this before, but no one in their right mind takes either fish oil or krill oil for its antioxidant capacity. For example, when you look at ORAC, the amount of krill the average person takes offers less than 5% of what might be considered the “DV” (or RDA) of antioxidants. We get orders of magnitude more antioxidants from fruits and vegetables (or other supplements). We take krill or fish oil supplements because they are great sources of DHA and EPA. And in that regard, they are virtually identical (subjective reports of diminished PMS symptoms in one study notwithstanding). Furthermore, most fish oil refiners add vitamin E to the oil as an antioxidant to give stability and add shelf-life, so the comparative shelf lives are also similar. I really don’t see one as being “better” than the other… instead, I see two alternative choices, either of which might represent the single best supplement choice you could make if you were only to take one supplement.

      1. Mark thanks for the feedback. Always hard for the amateur to sort through the hype and facts.

      2. A caveat about those ORAC scores… they’re specifically for water-soluble antioxidants and not oil-soluble ones like carotenoids (and fish oils). Therefore, you can’t universally compare antioxidant capacity using ORAC numbers alone.

  8. If you have problems with fish oil repeating on you during the day or making you uncomfortable, try taking the caps at night. That saved me.

  9. Fish oil kept repeating on me even when frozen, so I switched to krill oil. Big mistake for me. Nasty allergic reaction. (I have never eaten shellfish, never wanted to eat any, in fact had an aversion to it, now I know why.) Now I am taking an enteric coated fish oil with no problems.

  10. does pastured butter/cream contain omega-3 or is it mostly saturates?

    1. yes…the fat from animals raised on pasture is a good source of Omega 3 fatty acids. This includes butter from pastured cows! YAY!

      There is a significant drop in Omega 3 for every 5 days of grain feeding when ‘finishing’ an animal for market.

  11. I have been taking fish oil for a while now. Sometimes I do get the fish burps, but its no big deal. I do think, however, that it has caused my blood to thin. Is this normal? Is there something that I just need to deal with? Or is there any sort of remedy? I usually take about 2400 mg of DHA/EPA per day (or about 8 pills).

  12. another good source of Omega 3/6/9 in a good balance, esp. for people with fish allergy, is HEMP SEEDS and HEMP SEED OIL…just as with other Omega 3 & 5 supplements, don’t overdo it: approx. a 1/1 ratio daily = about 1 t. of each.

    and, a thought to consider with allergies in general: is it a true allergy, or is it a sensitivity, that may be corrected by correcting the Hydrochloric Acid levels in the stomach, with an appropriate HCL protocol

  13. Dairy products (butter, cheese etc.) form Ireland and New Zealand come from grassfed cows that do not recieve grain. In Ireland, it’s the law. It might be in New Zealand as well as I have never seen any that were not grassfed only products. These products are available in many stores if you look for them. Eggs from chickens raised on pasture in movable pens are also good sources of good fats.

    1. I buy New Zealand cheese from grass-fed cows at Trader Joes. Have bit with wine in the evening.

  14. I am really confused about fish oil vs. cod liver oil, or fermented cod liver oil.

    Also, my current supplements contain other omegas. Do I want to ditch those for just omega-3s?


  15. What about taking flax seed oil supplements? Wouldn’t they be just as beneficial yet wouldn’t be allergenic in someone with a shellfish allergy. I just like to play it safe!

  16. I take odourless fish oil to prevent repeating. Anyone know if this is any different from normal?

  17. I take flax seed oil as a supplement – nasty taste in liquid form so I add it to other drinks! You can also get Acai berries and Acai berry drinks which might be helpful – Acai berries have a high omega content apparently. Eggs are also available from hens fed a particular diet and so the eggs have a high omega 3/6 content. If you have an allergy to fish/shellfish then steer clear of supplements from these sources. There’s no guarantee that there won’t be contamination with a particular fish allergen and it’s better to be safe than sorry.

  18. As a Nutritional Therapist, here is what I would recommend for optimal health & healing ( which includes balancing cholesterol with all the factors ):500-650 mg. ALA; 300-350 mg. EPA; 200-250 mg. DHA; 200-250 mg. GLA. These are all contributatory to proper PROSTANGLANDIN development: hormone-like substances that keep inflammation in check.

    Keep in mind that most Cod Liver Oil is purified to REMOVE natural levels of A & D: we feel these components are BENEFICIAL, that naturally occuring A is not toxic at somewhat higher levels,and since A & D use the same receptor sites, the bodys’ innate knowing will choose appropriately. ALSO, my personal favorite is Green Pasture’s FERMENTED CLO w/ High Vit Butter Oil: provides factors to aide digestion, mitochondrial & neuro healing.

    1. After lots of research I changed from fish oil and cod liver oil pills that I had taken for years to the Green Pasture Fermented CLO and had a very nasty reaction. All over intense muscle aches and spasms that pretty much rendered me immobile. Now I find have been sensitised to fish oil in general and have not been able to go back to the pills I took before. I am miserable without it, but have read bad things about flax oil and don’t know what to sub for it. Others also have had reactions to the fermented oil, sometimes not at first but it gradually sneaks up on you and when it gets severe you don’t realize what has caused it, that was the case for me. So be careful with that supplement, it’s not for everyone.

      1. Two years since this comment, but I had a similar reaction to the Green Pastures Fermented CLO. And now am sensitised to all fish. Every time I try to eat a little fish be it fresh or tinned, salmon or white fish my entire system becomes inflamed, swollen, aching muscles and spasms and constipated for a week. Sadly, I also have a sensitivity to all seeds. But I can eat occasional walnuts and pecans. GREEN VEGGIES: At a conference a few years ago on preventative health, cardiologist Dr Caldwell Esselstyn and his wife (who have chosen to eat vegan and NO fat whatsoever, even from nuts and seeds) were promoting eating green leafy vegetables at every meal, that green vegetables contain enough Omega 3. What’s the latest science on omega 3 in green leafy veg?

  19. Thanks for the post Mark. I think I will give a good purified supplement a fair try. I will have my epi-pen standing by… 🙂

  20. If you have a fish oil allergy might want to look at Salvia Hispanica-L who’s common name is Chia. The best delivery system of Omega 3’s from the whole raw food Chia is a product Mila .

    1. Great idea on the chia – thanks!

      I was researching for something to give my fish-allergic ailing cat, who really seems to need some omega 3 supplementation. Flax oil would be rejected due to the bitter aftertaste, so I’m going to give the chia oil a try.

      1. I thought I was the only trying to find something to help an ailing cat with a fish allergy… Did you try the Chia oil and did it help?

  21. I have a fish oil allergy. I start to feel nauseous and. well, you don’t want to know what happens next!.. I started taking flax seed oil instead. Do you think this is a good comparison?

  22. I experienced spontaneous nosebleeds and lesions in my nostrils when taking both fish oil and krill oil at the recommended dosages. How common is this side effect?

    I assume this is due to excessive thinning of the blood. I have cut back on the dosage by 33% and the problem has been eliminated.

  23. Shellfish allergies may be due to the iodine that is bound to protein in the shellfish. It’s particularly high in scallops. I always thought I was allergic to iodine, till I communicated with Dr. David Derry from Canada who has done a lot of iodine research. It’s the iodine bound to a protein that I react to. According to the allergist I’m allergic to fish, but I’ve never had a reaction to it and finally started taking fish oil – no problem with it.

  24. I’m coming from a different direction. For years I thought my migraines were the result of a fish allergy. Turns out the problem was the aspartame in diet sodas and sugar-free gum that I was sensitive to. No migraines for over six months now, and I’m enjoying fish again. Good luck!

  25. I’m about to run out of my bottle of cod liver oil. Debating trying krill oil or regular fish oil.

    It seems with summer around the corner, regular fish oil might be the better way to go.

  26. Shellfish allergies may be due to the iodine that is bound to protein in the shellfish. It’s particularly high in scallops. I always thought I was allergic to iodine, till I communicated with Dr. David Derry from Canada who has done a lot of iodine research. It’s the iodine bound to a protein that I react to. According to the allergist I’m allergic to fish, but I’ve never had a reaction to it and finally started taking fish oil – no problem with it.

  27. I’m coming from a different direction. For years I thought my migraines were the result of a fish allergy. Turns out the problem was the aspartame in diet sodas and sugar-free gum that I was sensitive to. No migraines for over six months now, and I’m enjoying fish again. Good luck!

  28. Dairy products (butter, cheese etc.) form Ireland and New Zealand come from grassfed cows that do not recieve grain. In Ireland, it’s the law. It might be in New Zealand as well as I have never seen any that were not grassfed only products. These products are available in many stores if you look for them. Eggs from chickens raised on pasture in movable pens are also good sources of good fats.

  29. If you have a fish oil allergy might want to look at Salvia Hispanica-L who’s common name is Chia. The best delivery system of Omega 3?s from the whole raw food Chia is a product Mila .

  30. I stumbled on your website. I’m testing Krill oil, even though I am a lacto-ovo vegetarian and tested allergic to shell fish when I was a boy. This should be an interesting experiment and will let you know if there was a bumpy road for me after ingesting krill oil. Best wishes. WG

  31. I am extremely highly allergic to fish, shellfish… basically anything that comes from water, be it fresh or sea. If I have it, it will kill me.
    That being said, I was told to avoid any form of fish, seafood, shellfish. Algae is also a form that can cause an allergic reaction if you are like me, highly allergic to the point it will kill you. While they are high in fat, take the time to get to know walnuts if you’re not allergic to nuts. Walnuts carry a GOOD form of Omega 3. I have one serving a day and I’ve been extremely well because of it. Walnuts will also account for some protein intakes as well if you are worried about this. I haven’t found out yet if the walnut oil will give the same benefit.
    So if highly allergic, please be careful of your supplements. It isn’t much fun getting a shot of ephinephrine… not to mention the events that lead up to it.

    1. Thanks for your post. I too have a life threatening allergy to Seafood and anything that swims or lives in the water. I have just started the Paleo last month and have been wondering what should I be doing. I have been eating Walnuts, fresh ones— and haven’t done the flax oil or supplements yet. I have pondered the posts and some of them seem alittle over my head, but I shall keep reading!! Thanks again.

  32. Thank you~ I’m allergic fish, shellfish, eggs and latex. I will try the flax and seaweed

  33. I’m kind of the opposite of the OP. I am allergic to finned fish but not shellfish. If I eat finned fish, I am in the ER.

    So is krill still an option for me? I worry about cross-contamination in the facilities. Someone mentioned seal oil, but would that contain the allergens considering they live on a fish-based diet?

    I hate being allergic to fish 🙁 I know how great it is for me nutritionally.

    1. Did you figure out something that works? I’m in a similar “boat.”

  34. Try Lyprinol….seafood but proteins removed. I’m sensitive to seafood, but had no problem with this product.

  35. I know I’m late to the discussion but I wanted to thank you for the info in this post. I am one of the apparently few people who are deathly allergic to fresh water fish, mainly the oil. I’ve had some serious reactions just from being in the same room where fish is being fried. Trout, Bass, Salmon, etc. On the other hand seafood I consume with no problem, Crab being my favorite. I’ve always eaten omega rich eggs and lots of chia. This article helps and I am going to look into Krill oil. Thank you again for the info.

  36. Back to the allergy discussion, but from a different direction. I was given iodine dye in a hospital once, and am deathly allergic to it, yet I eat iodized salt regularly, and have eaten fish and shellfish all my life. Only once did I have any sign of a reaction – eating shrimp my lips swelled. Yet with the iodine dye I had an immediate anaphelactic shock, so it appears iodine was the issue. I have high cholesterol and trigycerides, and the occasional achy joint. I have avoided glucosamine and krill due to the ‘seafood’ issue, but wonder whether the risk isn’t simply to a high concentration of iodine. Can I safely take krill? I would love to do so, but have been afraid to try it.

  37. I have a strange reaction to fish oil and krill oil. I get heart palpitations, racing heart and feel woozy everytime I’ve tried to take even one gel cap of either. Doesn’t matter which brand I take either. I have high cholesterol (385) but also high HDL (86), low triglycerides, low C reactive protein. I did get horrible hives after eating just a little bit of crab meat a week after delivering my second son. The hives lasted a month and I’ve stayed away from it since. I had eaten crab previously with no issues.

  38. Finally, a possible answer to my symptoms! Never put two and two together until this morning! Have spots on my torso and even in my hair, swollen face, rash on face and eyes nearly swollen shut. Have been taking fish oils with no problems, but stated taking husbands Krill Oil as he has been raving about them. Happened to read on side of box that was facing away from me that it contains shellfish which I’m allergic too! Off to the doctor I will go….

  39. Hi,
    Someone please help. I am allergic to fish (and shellfish), nuts and seeds (incl fruit that have seeds like raspberries and kiwi, and so I am really seriously stumped as to what to do.

    I have Fibromyalgia and depression and am trying to come off Cymbalta as they clearly havent helped my depression at all. My research has shown that omega 3 – esp dha is beneficial for depression. But, can I find a source of supplements that wont kill me? Noooo!!!

    I can tolerate flaxseed oil capsules, but they contain omega 6 as well, and I don’t really want to increase my intake of that. BUT saying that, I am looking at a high strength dosage (I’m also a lady of larger than average proportions due to several years of disability)


    I am so sick of having pills thrown at me that really dont make any difference to either of my conditions, and feel that realistically, I need to try a nutritional approach after a lifetime of nutritional imbalance due to multiple allergies – seeing as everything else has failed.

    I’m at my wits end here.

    Many thanks in advance

  40. THANK YOU to everyone who posted here. This is the ONLY place where I’ve read about other people who’ve experienced violent cramping with fish/krill oil.

    When I’ve taken any fish oil or krill oil, I develop violent all-over muscle cramping, which can last for 4 or 5 hours. The only thing that stops the cramping is to take tons of CoQ-10 (Qunol works fabulously for me), and wait for it to get digested. And also take lots of magnesium, and drink lots of water.

    Now I have some good alternatives: walnuts, ground flax and flax oil, chia seeds (and Chia OIL?). Also my deep thanks to Mark Sisson for explaining that the trigger may be the fish proteins. As I absolutely HATE all fish, in retrospect, I should have known their oils would not be good for me.

    When I told various nutritionists, the CDC, my own doc and the krill oil manufacturer, EVERYONE could not understand why I had the reaction, telling me they’d never ever heard of such a thing. Plus, my all-over cramps/spasms were occurring over a 3-week duration, until I found the CoQ-10 antidote, which actually stopped them for good.

    So thank you again for solving a very frightening problem for me. BTW, I am a 60-yr old woman with very high cholesterol and triglycerides, almost-normal LDL and very low HDL. I take 120 mg of Armour Thyroid.

    The only other time I get the full-body all-night cramps is when taking ANY kind of big-pharma-cholesterol meds. Right now I’ve just begun using organic apple cider vinegar and concentrated cherry juice plus a session of Niacin-flush daily, since I can tolerate that.

    My diet is mostly all kinds of vegetables and as I love dark green leafy things I eat tons of them, some but not a lot of grains, some fruits, not much sweet stuff and very little dairy. I’m shocked that my cholesterol levels are so high. Every 3 weeks I need to eat meat, not vegetable-protein sources… so I do. Mostly red meat, a pound over a few days, and then am restored. I do eat ground flax seeds, have come to love flax oil, use coconut oil, eat ground pumpkin seeds and chia seeds (but perhaps not enough — a few teaspoons per day).

    I’ve jumped in and commented here without reading up on the Primal Diet so my statements may be uninformed. But I am so glad to have found you!

  41. Hi All –

    I am allergic to fish, some tree nuts, and vegetables of certain families, so I understand the challenge of finding appropriate sources of omega-3 fatty acids. If you are allergic to fish, I would be very cautious about taking fish oil pills. Yes, fish oil pills are theoretically all lipid and no protein, but this may vary by brand. Also the study mentioned by Mark was done on only 6 patients. To my limited knowledge, there have been no wide investigations into fish oil effects on people with fish allergies, so the evidence is limited. Also, here is a link to a documented case of someone with a crab allergy experiencing anaphylaxis after taking a fish oil pill The existing body of very limited evidence suggests that fish oil pills are OK, but again the experiment was done on only 6 people!

  42. I have a severe seafood allergy and never knew what to do about increasing EPA and DHA due to this. Omega 3 is recommended in patients with diabetes to control blood glucose. It is also recommended in patients with pre diabetes and I personally would recommend Omega 3 to patients with a risk factor to diabetes, such as having a first degree relative with either type 1 or type 2 diabetes. Thanks

  43. I’m interested in how a women with a severe fish allergy supported a healthy pregnancy. Does anyone have experience with sever fish allergy and pregnancy?

    Thank you!