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Red Tide Blooms

Aquatic Toxins Program

dead fish on beachAs red tide blooms approach coastal areas, breaking waves can cause their toxins to become mixed with airborne sea spray. People in coastal areas can experience varying degrees of eye, nose, and throat irritation. When a person leaves an area with a red tide, symptoms usually go away. People with severe or chronic respiratory conditions such as asthma or chronic lung disease are cautioned to avoid areas with active red tides.


  • Respiratory and Skin Irritation
  • Transmission
  • Information about Beach Conditions
  • Red Tide Frequently Asked Questions
  • Additional Information

One of the most frequent symptoms people experience during a Karenia brevis (also known as K. brevis) red tide is respiratory irritation. If you have ever visited a beach during a red tide, you may have experienced the "red tide tickle" which can include itchy throat and coughing. Brevetoxins, chemicals produced by K. brevis, may also irritate pre-existing respiratory conditions including asthma, bronchitis and/or chronic lung disease. Persons with asthma are advised to bring their inhaler to the beach during a red tide or avoid the area until conditions improve. Some swimmers experience skin irritation and rashes after swimming in waters with a severe red tide. They have also reported eye irritation from the sea foam. In some red tides, dead fish and other sea life may wash ashore; during these conditions, it is advised that beachgoers avoid swimming in water where dead fish are present and if experiencing respiratory irritation, leave the beach area.

Shellfish like clams, oysters, and coquinas that are harvested from areas near or in active red tides should not be eaten. These shellfish are filter feeders that can concentrate the toxins. Scallops can be consumed if only the scallop muscle is eaten. Scallop stew, using the whole animal including guts, should not be eaten. Seafood, also commonly called shellfish such as crabs, shrimp, and lobster can be eaten because they do not concentrate the toxin. However, the hepatopancreas or “tomalley” should be discarded. Please visit the Florida Department of Agriculture and Consumer Services website (opens in new window) to check where approved shellfish harvesting beds are located and if they are open for harvest. 


To see what the red tide conditions are like before going to the beach, visit Florida Fish and Wildlife Conservation Commission Research Institute Red Tide Conditions Report.

To see if and where red tide is occurring in Florida, please visit Mote Marine's Beach Conditions Report.

Frequently Asked Questions: Red Tide

What is red tide?
A red tide is a higher-than-normal concentration of a microscopic alga (plantlike organism). In the Gulf of Mexico, it is Karenia brevis, often abbreviated as K. brevis. At high concentrations, the organisms may discolor the water, sometimes red, light or dark green, brown or the water may appear clear.

What causes red tide?
A red tide bloom develops when biology (the organisms), chemistry (natural or man-made nutrients for growth) and physics (tides, winds, currents) work to produce the algal bloom. No one factor causes the development of a red tide bloom.

Where can I check the status of red tide at my local beach?
Florida Fish and Wildlife Conservation Commission (FWC) (opens in new window)
Red Tide Current Status and Mote Marine Laboratory (opens in new window)

Are red tides new?
No. Red tides were documented in the Gulf of Mexico as far back as the 1700s and along Florida's Gulf Coast since the 1840s. While red tides and other algal blooms occur worldwide, K. brevis is found almost exclusively in the Gulf of Mexico but has been found on the east coast of Florida and off the coast of North Carolina.

How long does a red tide last?
Red tide blooms can last days, weeks or months, and can also change daily due to wind conditions and ocean currents.

Is it safe to swim in water affected by red tide?
While people swim in red tide, some individuals may experience skin irritation and burning eyes. If your skin is easily irritated, avoid red tide water. If you experience irritation, get out of the ocean and thoroughly wash off with fresh water.

Can red tide affect me when I am not on the beach?
People in coastal areas near the shoreline may experience varying degrees of eye, nose, and throat irritation.  When a person leaves an area with red tide, symptoms usually go away. If symptoms persist, please seek medical attention.

Are there people who are more sensitive to the toxins caused by red tide?
People with respiratory problems (like asthma, emphysema or bronchitis) should avoid red tide areas, especially when winds are blowing on shore. If you go to the beach and have one of these conditions, you should be very cautious. If you have symptoms, leave the beach and seek air conditioning (A/C). If symptoms persist, please seek medical attention.

What can I do to lessen the effects of red tide?
People usually get relief from respiratory symptoms by being in air-conditioned spaces. This is also true when driving: keep your car windows up and the A/C or heat on. For people without asthma or any other chronic respiratory problems, over-the-counter antihistamines may relieve symptoms. People with chronic lung ailments should be especially vigilant about taking prescribed medications daily. Always seek medical care if your symptoms worsen.

Can red tide affect pets?
Just like people, pets may be affected by red tide. If you live close to the beach, consider bringing outdoor pets inside during a bloom to prevent respiratory irritation. If you are at the beach with your pets, do not allow them to play with dead fish or foam that may accumulate on the beach during or after a red tide. If your pet swims in the red tide, wash them off with freshwater as soon as possible.

Is Seafood in the Area Safe to Eat?
Clams and oysters (mollusks) can contain red tide toxins that cause Neurotoxic Shellfish Poisoning. Check local harvesting status before collecting at Finfish caught live and healthy can be eaten if filleted and rinsed thoroughly. Edible meat of crabs, shrimp and lobsters (shellfish) can be eaten (do not eat the tomalley - the green digestive gland - of shellfish). Do not eat distressed or animals found dead under any circumstances.

Where can I get more health and safety information on red tide?
Florida Department of Health
The Centers for Disease Control and Prevention (opens in new window)

The location of current red tide events within Florida coastal waters as well as links to more detailed information about red tide organisms can be found on the Fish and Wildlife Research lnstitute  (formerly the Florida Marine Research Institute) home page. For more information on red tide and beach conditions in Sarasota County, visit: Our Gulf Environment 

Red Tide Rack Cards

Red Tide Rack Card, English

Red Tide Business Card, English

Information on Florida Red Tides and Their Toxins, English

Red Tide Rack Cards in Other Languages






Red Tide Business Cards in Other Languages






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