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Sargassum (Seaweed)

Florida Department of Health in St. Johns County Environmental Public Health Program

Brown Alga (Seaweed) - Sargassum 

Sargassum is a seaweed that washes up on Florida beaches, the Gulf of Mexico, and the Caribbean islands. As it decomposes, it releases a substance called hydrogen sulfide, which has an unpleasant odor like rotten eggs.

Although the seaweed is not a toxin-producing algae and will not harm your health, tiny sea creatures living in Sargassum may cause skin irritations.

Learn more about Sargassum—what it is, how it could impact your health, and how to protect yourself and others from possible health effects.

What is Sargassum?

Sargassum is a naturally occurring seaweed that originates offshore in the Atlantic Ocean and floats freely on the ocean surface. It is abundant in the Atlantic Ocean and the Gulf of Mexico. In recent years, large quantities have come inshore on Florida’s beaches. Sargassum provides a habitat for an array of animals such as crabs, shrimp, sea turtles, and fish but in large quantities, it can be a nuisance and an eyesore, impacting tourism and recreational enjoyment of beaches.

Why does Sargassum smell so bad?

When washed ashore, the decomposition of Sargassum seaweed causes the production of hydrogen sulfide gas, and smells like rotten eggs.

Can hydrogen sulfide affect my health?

Hydrogen sulfide can cause eye, nose and throat irritation, other health effects are not expected. If you have asthma or other breathing ailments, you may be more sensitive to hydrogen sulfide and may experience difficulty breathing after inhaling it.

Why is Sargassum a Concern?

  • The tiny sea creatures that live in Sargassum may irritate skin with direct contact.
  • Decomposing Sargassum causes an unpleasant smell due to the release of hydrogen sulfide gas.
  • While people with prior respiratory conditions may be more sensitive to the hydrogen sulfide gas, in open areas, like beaches, the general public should not experience any adverse health impacts. Sensitive populations should consider taking precautions to minimize their exposure.

Does Sargassum cause skin rashes and blisters?

Sargassum itself does not sting or cause rashes. However, tiny organisms that live in Sargassum (like jellyfish larvae) may irritate the skin if in you come into contact with it.

Can I cook with Sargassum?

No. You should not use Sargassum in cooking because it may contain high levels of heavy metals like arsenic and cadmium.

How can I protect myself and my family from exposure to Sargassum?

  • Always supervise children at the beach.
  • Avoid touching or swimming near seaweed. Organisms that live in the seaweed may sting and cause skin irritation.
  • Use gloves if you must handle seaweed.
  • Stay away from the beach if you experience irritation or breathing difficulties from hydrogen sulfide, until symptoms go away.
  • Close windows and doors if you live near the beach.
  • Avoid or limit your time on the beach if you have asthma or other respiratory problems.

Will hydrogen sulfide from Sargassum cause cancer or other long-term health impacts?

Hydrogen sulfide is not known to cause cancer in humans. People with prior respiratory conditions may be more sensitive and may experience distressed breathing.

Learn More About Sargassum

  • Sargassum is common in the Sargasso Sea, a region of the North Atlantic Ocean that is surrounded by four currents but no land.
  • Florida has no regulatory guidelines for exposure to hydrogen sulfide at the beach since it is not expected to harm health.
  • Odors from most substances in outdoor air are not at levels that can harm your health.
  • If workers are collecting and transporting Sargassum, they should wear personal protective equipment, such as gloves, boots, and gas filter half masks

If you have questions or comments about Brown Alga (Sargassum), we encourage you to contact:

Please write to:

Division of Disease Control and Health Protection
Bureau of Environmental Health, Public Health Toxicology
Florida Department Health
4052 Bald Cypress Way, Bin # A-08
Tallahassee, FL 32399

Or call:

Public Health Toxicology Toll free at: 877-798-2772