Red Tide and Asthma: Avoid the Beach During Harmful Algae Blooms

Red Tide Algae:

Red tide is an overgrowth of a type of ocean algae, Karenia brevis (K brevis). It tends to be more concentrated along Gulf of Mexico shorelines and can produce highly potent airborne toxins called brevetoxins. Not all red tides are harmful though, so a more correct term is "harmful algae blooms", also known as HAB for short.

How You Can Be Exposed:

K brevis grows in certain waters just offshore along the Gulf of Mexico, especially Florida. At certain times of the year, the levels of this algae rises, producing toxic levels of airborne fumes. If you visit the beach for an hour or more during these times, then you may notice symptoms.

What Happens When You Are Exposed to HAB:

HAB toxins often lead to eye irritation, nasal symptoms, a dry cough, and wheezing even in people who don't have asthma. These symptoms generally go away once they leave the beach area. But for people who have asthma, the symptoms are usually much more severe. Plus, they don't go away as quickly.

New Study Examines Red Tide's Effect on Asthma:

Researchers from seven organizations were involved, including the National Institute of Environmental Health Sciences (NIEHS), Centers for Disease Control and Prevention, Children’s Hospital Medical Center and University of Cincinnati, Florida Department of Health, Harbor Branch Oceanographic Institution, Lovelace Respiratory Research Institute, and the University of North Carolina.

• Ninety-seven patients with asthma, all residents of Sarasota, Florida, were studied.


• Patients spent at least an hour at affected beach areas, both during times when the red tide toxins were active and times when they were not.

• Data was gathered for the study through medical history questionnaires, nasal swab sampling, and lung function testing (spirometry).


• When the red tide blooms were active, patients reported a marked increase in symptoms, especially chest tightness. Lung function testing also revealed a decrease in lung function. Those same changes did not occur when the HAB toxins were not in the air.

If You Live in Gulf Coastal Areas:

Patients with asthma who live near affected beach areas year-round reacted less intensely to the red tide toxins during bloom periods. Researches speculate that coastal residents, who had less of a reaction to the toxins, have learned not to get exposed or may use more asthma medications to deal with red tides. Additional explanation may be that coastal residents were already affected by the toxins because they had been exposed to them regularly even before the study. As a result, they reacted less to the one-hour beach exposure

How to Prevent Red Tide Asthma Attacks:

If you have asthma and are planning a visit to the Florida Gulf Coast beaches, you may want to take steps to reduce your exposure during times when red tide levels are at their highest. Patients with asthma can stay informed of Florida red tide conditions by checking with local environmental groups, including the Florida Department of Health and the Florida Marine Research Institute. In this way, you can help to avoid red tide-induced asthma attacks.

In Summary:

If you have asthma and live near the Gulf coast or plan to visit there during periods when red tide toxins or other harmful algae blooms are at high levels, you may want to talk with your physician about modifying your asthma action plan to include red tide toxin-related action steps.

Sources: Fleming LE et al. "Aerosolized Red-Tide Toxins (Brevetoxins) and Asthma." Chest 2007; 131:187-194. Related press release available at: <http://www.chestnet.org/about/press/releases/2007/010807_1.php>http://asthma.about.com/od/signssymptomsofasthma/p/managesymptoms.htm