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The Truth About Sea Moss Side Effects

 Sea moss side effects

Sea moss is the new superfood everyone’s talking about. The Atlantic red seaweed, also known as Chondrus crispus and Irish moss, is packed with healthy nutrients and shows great promise in preventing and treating numerous health conditions.

If you're into healthy nutrition, you've already heard of sea moss’s health benefits. We're now here to tell you the truth about its potential side effects.

Don’t worry. Most people are fine taking sea moss. Chondrus crispus is safe, and possible side effects are either mild or rare. Yet, we believe you should be aware of them before introducing sea moss into your diet.

So, here’s an honest disclosure and complete list of all possible side effects of consuming sea moss.

Related article: What are the health benefits of sea moss?

Sea Moss Common Side Effects

Introducing a new ingredient into your diet often requires some adjustments, even when it's 100% natural. The same goes for sea moss.

Chondrus crispus is generally safe, and most people don't experience discomfort or side effects. Nevertheless, it's not uncommon for sea moss to cause mild side effects, especially gastrointestinal ones, including:

  • Eating sea moss can make you feel gassy or bloated at first, but the bloating usually goes away once your body gets used to it. Indeed, most people find that these side effects stop after two weeks.
  • Sea moss makes you feel full. It's loaded with fibers, and a tiny bit of Irish moss can kill your appetite. It's a good thing if you're on a weight-loss diet. Otherwise, it’s better to take it at night.
  • It can have a mild laxative effect due to its high magnesium and fiber content. However, it should not cause diarrhea. Diarrhea is often a sign you're overeating sea moss. 
  • Some people report constipation. Everyone's physiology is unique, and while sea moss may be laxative for some, it can constipate others. Usually, gastrointestinal side effects disappear once your body gets used to sea moss.
  • It may make you feel nauseous. Nausea is a rare but possible side effect of sea moss. It's often a sign of overconsumption or a bad batch of sea moss. People who take sea moss in the morning on an empty stomach are more prone to feel nauseous than people who take it a night.
  • Sea moss gel may cause skin reactions when applied topically. Sea moss gel is excellent for the skin, but some people may not tolerate it well and experience itching, redness, or others.

Although rarely, sea moss may also cause the following mild or severe side effects: headaches, vomiting, low blood pressure, high blood pressure, low blood sugar, fatigue, hyperthyroidism, iodine poisoning, heavy metal intoxication, allergic reactions, etc.

How to avoid most sea moss side effects? 

Most sea moss side effects are down to taking too much of it or poor-quality products. Here are a few tips to keep bowel disturbances and other  side effects at bay when starting with sea moss:

  • Start with a low dosage. Sea moss is a very nutrient-rich food; some bodies need more time than others to adjust to it. So take only half a tablespoon during the first few days and gradually increase the dosage. You'll avoid most gastrointestinal discomforts when beginning with sea moss.
  • Never exceed sea moss’s daily recommended intake. Most sea moss's side effects are caused by overconsumption. Like any superfood, Irish moss has numerous health benefits but must be taken in moderation. We usually recommend that our clients take two tablespoons of sea moss gel daily.
  • If sea moss makes you nauseous or kills your appetite, consider taking it at night before bed rather than in the morning on an empty stomach. 
  • Avoid eating raw or dehydrated sea moss if you experience discomfort and side effects. Sea moss gel or capsules are easier to digest and often cause fewer bowel disturbances. 
  • Make a patch test if you’re worried you may be allergic to sea moss.
  • Only consume high-quality organic wildcrafted sea moss tested for heavy metals. Avoid fake pool-grown sea moss.

Besides the above common mild side effects, sea moss may also cause severe health concerns. They're infrequent, but we believe you should be informed.

Warnings About Sea Moss Severe Side Effects

Although very rare, sea moss may also cause some severe side effects that can potentially threaten one's life. Iodine poisoning is the main concern here, but once again, it comes down to eating way too much sea moss. Like with any food, allergic reactions are possible. You should also be aware of heavy metals that can be found in sea moss and other seaweeds. 

Iodine poisoning and hyperthyroidism

Iodine poisoning is probably the most severe potential sea moss side effect but can only occur if you ingest excessive amounts of it.

With an average of 47 mcg per serving (2 tbsp), Chondrus crispus is one of the foods with the highest iodine content. One serving accounts for about 30% of the daily iodine intake recommendations for an adult (150 mcg per day – increased to 250 mcg for pregnant or breastfeeding women).

Iodine is an essential mineral for the body and thyroid function. But while iodine deficiencies can cause serious health problems, the excess is also dangerous.

Mild symptoms of iodine poisoning include diarrhea, nausea, vomiting, or a burning sensation in the mouth. Severe symptoms include airway swelling, difficulty breathing, weak pulse, cyanosis, and even coma in the most extreme cases. It can also lead to hyperthyroidism (overactive thyroid function), a serious health condition causing numerous complications. 

Iodine poisoning is extremely rare. According to the National Institute of Health, the safe daily upper limit of iodine for adults is set at 1,100 mcg. That includes all sources (sea moss and other seaweeds, fish, shellfish, dairy, eggs, iodized salt, liver, chicken, and eventual iodine supplements).

To reach toxic levels of iodine, one would need to ingest more than 20 times the daily recommended dosage of sea moss. So, while iodine poisoning is a potential warning for sea moss consumers, it’s very unlikely to happen if you stick to the recommended daily dosage.

Sea moss allergies 

Like with any food, allergic reactions[1] are another possible side effect of sea moss. But seaweed allergies are rare, and ocean plants contain few allergens.

People with seafood and shellfish allergies can generally take sea moss. This is because seaweeds do not contain any fish proteins (the primary allergen in seafood). But ask your doctor's advice before taking sea moss if you have a seafood allergy.

Allergy symptoms may occur up to 48 hours after ingesting sea moss or applying its gel to your skin. They range from mild to severe and include rashes, swelling, itching, sneezing, breathing difficulty, hives, and anaphylaxis in the worst cases.

If you’re worried you may be allergic to sea moss, make a patch test or contact an allergist to run allergy tests before taking sea moss for the first time. Immediately stop and seek medical attention if you experience any allergy symptoms after eating Irish moss or applying gel on your skin.

Related article: Can sea moss help with allergies?

Heavy metals in seaweeds

Heavy metals are another risk associated with sea moss. Metals are everywhere in our environment (air, water, and soil). Ingesting high levels of heavy ones, like mercury, lead, arsenic, or cadmium, is dangerous for your health. 

Ocean products like fish, shellfish, and edible seaweeds[2] often contain heavy metals (mainly mercury). Depending on where it grows, sea moss can absorb and retain heavy metals from polluted waters.

Heavy metals may have severe toxic effects, including gastrointestinal and kidney dysfunction, nervous system disorders, vascular damage, and immune disorders. In addition, heavy metals can be harmful to pregnant or breastfeeding women.

The easiest way to keep these dangers and side effects at bay is to purchase premium-quality sea moss products guaranteed with the safest levels of heavy metals.

A third-party laboratory tests all products sold at Organics Nature.

Who Should Not Take Sea Moss?

Sea moss is a safe product to consume. Its common side effects are mild, and more serious ones are rare. However, some people should not consume it without their doctor's approval and supervision:

People with thyroid disorders

Because of its high iodine content, sea moss may considerably impact thyroid function. Therefore, people with thyroid disorders, including hypothyroidism and hyperthyroidism, should not take sea moss without medical supervision.

Excessive iodine intake may aggravate their problems. Besides, sea moss can interfere with thyroid medications.

People who take blood thinners or blood pressure medications 

Sea moss is one of the best plant sources of omega-3 fatty acids and is beneficial for heart health. It helps lower the risk of heart disease, prevent blood clots and high cholesterol, and may help reduce blood pressure. 

However, because of its potent anticoagulant and blood-thinning properties, people who take blood-thinner medications should avoid consuming sea moss. It can interfere with your medications and increase the risk of bleeding.

People with iodine intolerance

Iodine intolerance, or iodine allergy, is extremely rare but can lead to anaphylactic shock and be fatal. Do not take sea moss if you've been diagnosed with iodine intolerance. It’s one of the foods with the highest iodine content.

Pregnant or breastfeeding women

Sea moss is safe for pregnant and breastfeeding women if consumed in moderation. It’s even packed with pregnancy-supporting nutrients and can be combined with prenatal vitamins.

However, because of its high iodine content, pregnant and breastfeeding women must carefully control how much sea moss they eat daily. While you need iodine supplementation during pregnancy, the excess may be dangerous for your baby's health. Pregnant women must also pay special attention to heavy metals found in poor-quality sea moss products. Make sure to purchase sea moss that's been tested and guaranteed safe!

Related article: Can you take sea moss while pregnant or breastfeeding?

Babies, children, and toddlers

Sea moss is generally safe for babies and children. It's even beneficial for them too. But you must adjust the dosage to their age, weight, size, and iodine intake.

Sea moss side effects: FAQs

Incorporating Irish moss into your family's lifestyle can raise a few more questions. Our team of experts answers the frequently asked ones here. Do not hesitate to ask yours in the comment section below, and we'll reply shortly.

Is sea moss FDA-approved?

No, like any over-the-counter food supplement, sea moss is neither FDA-approved nor FDA-regulated in any of its forms (raw, gel, powder, gummies, capsules, etc.). It's currently under research, and more studies must be conducted before it becomes FDA-approved.

Meanwhile, we invite you to be careful and only buy sea moss products from reliable companies.

What are the side effects of fake sea moss? 

Fake sea moss is the seaweed that's been pool-grown instead of wildcrafted. It usually contains minimal nutrients compared to natural sea moss. While there are no specific dangers to eating fake sea moss, the nutritional benefits are limited.

Can sea moss make you sick? 

Sea moss should not make you sick. Some mild side effects that may occur when you're taking it for the first time include bowel disturbances and nauseous feelings. Most of the time, these discomforts go away after a few days or weeks.

If sea moss makes you sick, it may be a sign you’re taking too much of it and have symptoms of iodine poisoning (see above). Make sure not to exceed the recommended daily dosage. Your body may not adjust to sea moss. If symptoms don’t go away, stop taking it.

Can you take sea moss with medications?

Sea moss is a 100% natural product. Yet, it’s very potent. People who take the following types of medications should not take sea moss without medical supervision:

  • Blood thinners
  • Blood pressure medications
  • Diabetes medications
  • Thyroid medications

Sea moss may interfere with other medications we’re not aware of. So if you're taking drugs, always ask your doctor's advice before eating sea moss.

Can you take sea moss with alcohol? 

There is no known contra-indication of taking sea moss with alcohol. But we encourage you to try sea moss as part of a healthy diet to reap the most of its benefits.

Related article: 10 great sea moss drink ideas


[1] Seaweed allergy, Iason Thomas, MRCP , Leonard Q.C. Siew, MRCP, PhD , Timothy J. Watts, MRCP , Rubaiyat Haque, FRCP , November 21, 2018. DOI:

[2] Metals in edible seaweed. Rubio C, Napoleone G, Luis-González G, Gutiérrez AJ, González-Weller D, Hardisson A, Revert C.. Chemosphere. 2017 Apr;173:572-579. doi: 10.1016/j.chemosphere.2017.01.064. Epub 2017 Jan 12. PMID: 28152409.


  • Dear Fuzzy,
    Sea moss gummies are low dosage and generally very safe to take. However, if you’re taking any medication, we recommend asking for your doctor’s advice first, as we do not know about possible interactions between sea moss and Losartan.
    Warm regards,
    Organics Nature

    Organics Nature
  • Dear Michelle,
    Sea moss gel is a perishable product and bad batches may happen, especially if you make it yourself.
    If you suspect you have a bad batch, we recommend not using it. Usually, you can tell by the smell, color, or appearance. The gel usually last for about a month when refrigerated. You can learn more about how to store sea moss properly in our related article here:
    Warm regards,
    Organics Nature

    Organics Nature
  • Dear Lorraine,
    We’re happy you’re giving it a try! Looking forward to hear about your experience!
    Warm regards,
    Organics Nature

    Organics Nature
  • Hi, im taking 50 mg of Losartan potassium, for my blood pressure is it ok to take sea miss gummies?

  • If you think that you have a bad batch of sea moss gel what should you do?


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