Overview

Sea moss, or Irish moss, is a type of seaweed called Chondrus crispus. The fronds of sea moss are used to make dietary supplements and oral gels. People take sea moss for many reasons, but its benefits are not well defined. It may cause constipation, diarrhea, or upset stomach. Before taking sea moss, make sure to tell your health care provider about all of your health conditions and any medicines or supplements you may be using. In particular, tell your health care provider if you have thyroid problems or are taking any products that contain iodine.

Uses

What is sea moss used for?

Sea moss (Chondrus crispus) is used for many reasons, although its benefits are not well defined. Some common reasons for using sea moss include the following.

• To improve gut and digestive health
• To improve the health and appearance of the skin
• To increase iodine levels

Note: The FDA has not reviewed sea moss for safety and effectiveness. Learn more about dietary supplements here.

Sea moss is available as a dietary supplement in various strengths and dosage forms. It is also included in products that contain other ingredients, such as kelp, seaweed, or burdock.

How does sea moss work (mechanism of action)?

Sea moss, also known as Chondrus crispus, is a form of red seaweed that grows on rocks in the Atlantic ocean. It is also commonly known as Irish moss or red moss. Products that contain sea moss are usually made from its fronds (leaf-like structures). Sea moss contains carbohydrates, fiber, vitamins, and minerals. It also contains carrageenan, a fiber that is commonly used to thicken foods and drinks.

The fiber in sea moss may help increase the growth of healthy bacteria in your gut and slow down the growth of bad bacteria. This has led to interest in taking sea moss to improve digestion and gut health. But there may not be enough fiber in sea moss to have this effect, and its benefits for this use are not well defined.

Sea moss contains many nutrients that are thought to help with overall health and skin health. But it is not clear if sea moss or these nutrients are helpful for improving skin health or other health problems.

Sea moss can contain very large amounts of iodine, depending on where it was grown and how the product was processed. Iodine is a mineral that your thyroid uses to make thyroid hormones. In the U.S., most people get enough iodine from their diet and iodized salt. The amount of iodine found in sea moss may vary, and taking too much iodine can be dangerous. Speak with a health care provider if you think you need an iodine supplement.

Sea moss naturally contains many chemicals and nutrients. The amounts of each substance in a specific sea moss product may vary. Some, none, or all of these substances may have effects on the body. These effects may change depending on how much of each substance is found in the product you are using.

How should I store sea moss?

You should store sea moss according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of sea moss?

The most common side effects of sea moss are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

• Constipation or diarrhea
• Upset stomach

There may be other side effects of sea moss that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of sea moss?

While less common, the most serious side effects of sea moss are described below, along with what to do if they happen.

Severe Allergic Reactions. Sea moss may cause allergic reactions, which can be serious. Stop taking sea moss and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Thyroid Problems.Sea moss contains iodine. Large amounts of iodine can cause the function of your thyroid gland to change. This can raise your thyroid hormone levels (hyperthyroidism), lower your thyroid hormone levels (hypothyroidism), or cause your thyroid to grow larger (thyroid goiter). These problems are more likely to happen when iodine is taken regularly at doses higher than the recommended daily intake. Tell your health care provider if you have any of the following signs of thyroid problems.

• Weight gain or weight loss
• Feeling unusually cold or hot
• Tiredness that does not go away or continues to worsen
• Mood swings
• Trouble sleeping
• Constipation
• Tightness in your throat
• A hoarse voice

Iodine Poisoning.Sea moss contains iodine. People who regularly take large amounts of iodine may develop iodine poisoning. This is sometimes called iodism. To reduce the risk of getting iodine poisoning, do not take more iodine than the recommended daily intake or the amount recommended by your health care provider. Stop taking sea moss and call your health care provider right away if you have any of the following symptoms of iodine poisoning.

• Sore gums or teeth
• Bad headaches
• The whites of your eyes seem red
• Swollen eyelids
• Blurry vision
• Your eyes water, your nose runs, or you have more saliva in your mouth than usual

Precautions

Who should not use sea moss?

Allergies to Ingredients. People who are allergic to any of the following should not take sea moss.

• Red seaweed
• Sea moss
• Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific sea moss products they stock.

What should I know about sea moss before using it?

Sea moss is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep sea moss out of the reach of children.

Sea moss contains iodine. You can get iodine from several places, including foods and vitamins or supplements. Many multivitamin and combination supplement products have iodine in them. It is important not to take too much iodine, as this can be harmful. If you are not sure how much iodine you need, talk to your health care provider.

Sea moss is available in many forms, including a gel, a powder, and capsules. Each of these forms may contain different amounts of the chemicals and nutrients that are naturally found in sea moss. Many of these products also contain other ingredients. Read the product label carefully to understand which ingredients it contains.

If you are taking sea moss gel, use an accurate measuring device to measure your dose. Read the product label closely, and follow the instructions. Most sea moss gels should be mixed with foods or drinks.

Herbal products, such as sea moss, naturally contain many chemicals. The amount of each chemical in a specific sea moss product can change for many reasons, including the weather and light where the seaweed grew, the time of year when it was harvested, and the way that it was processed after it was harvested. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Talk to your health care provider if you have questions or concerns.

Sea moss may absorb toxic substances from the waters where it grows. These toxic substances, which include arsenic, mercury, and lead, may be found in some sea moss dietary supplements. The FDA has not tested sea moss products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using sea moss?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if sea moss is right for you.

In particular, make sure that you discuss any of the following.

Thyroid Problems.Sea moss contains iodine. Taking large amounts of iodine may change the way the thyroid works. This could make some thyroid problems worse. Tell your health care provider if you have any thyroid problems, such as high or low thyroid hormone levels, thyroid nodules, a thyroid goiter, autoimmune thyroiditis, or Graves’ disease. See the Side Effects section for more details.

Other Medicines and Supplements.Sea moss may interact with other medicines and supplements. Before taking sea moss, tell your health care provider about any prescription or OTC medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how sea moss could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. Some of the nutrients in sea moss, such as iodine, pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does sea moss interact with foods or drinks?

There are no known interactions between sea moss and foods or drinks.

It is unknown if drinking alcohol will affect sea moss.

Does sea moss interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking sea moss.

• A thyroid medicine, such as levothyroxine, which is used to raise thyroid hormone levels
• An antithyroid medicine, such as methimazole or propylthiouracil (PTU), which is used to lower thyroid hormone levels
• Lithium, which is a medicine for certain mental health conditions
• Any other product that contains iodine, such as iodine supplements, potassium iodide, or iodine/potassium iodide (Lugol’s solution)

The interactions between sea moss and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with sea moss is incomplete. Always check with your health care provider before taking sea moss with any medicines.

Dosing

What should I do if I accidentally use too much sea moss?

If you or someone else has used too much sea moss, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Read the product label closely, and speak with a health care provider about how to take sea moss safely. Do not take double or extra doses, even if you miss a dose.