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Red Tide especially troublesome for asthma, allergy patients

Most Floridians know Red Tide is here when the smell of dead fish fills the air.

Seen in oceans around the world, Red Tide occurs almost annually, but not always in high levels. The last time Florida experienced a big Red Tide bloom was almost 10 years ago. But scientists are now tracking a patchy bloom 5 miles offshore in southern Pasco and northern Pinellas counties.

When Red Tide does reach our beaches again, many people who suffer from allergies and asthma will know.

Algae are vital to our ocean ecosystem, but under certain environmental conditions, the algae known as Karena brevis (k. brevis) can grow quickly, creating large blooms that turn the ocean a reddish-brown color and producing toxins that can be harmful to sea life and humans. This phenomenon is known as Red Tide. Brevitoxins, a by-product of Red Tide, can cause problems when ingested or inhaled, and they can kill a large number of fish and negatively affect shorelines.

Brevitoxins tend to accumulate in shellfish. When ingested they can cause neurotoxic shellfish poisoning, which causes gastrointestinal symptoms as well as neurologic ones, such as tingling in fingers and toes. Be cautious when ingesting shellfish during Red Tide season — typically summer, when warm water contributes to the phenomenon — but note that the state of Florida closely monitors shellfish beds in Red Tide areas and closes them until shellfish are safe to eat again.

The symptoms of ingesting seafood contaminated with Red Tide are well documented, but the effects of inhaling brevitoxins are less clear. Anecdotal evidence points to upper and lower respiratory tract irritation. In my experience, patients with asthma or allergies are more likely to experience symptoms with Red Tide exposure. These include itchy and burning eyes, throat irritation and nasal symptoms like congestion, sneezing and itching. Coughing, wheezing and chest tightness also have been reported. Asthmatics might experience setbacks after previously stable asthma, requiring more intensive treatment. Many patients also report that their skin stings or burns, or they get a rash, when they come in contact with infected seawater.

If you know that Red Tide has reached our shores, exercise caution. If you have known allergies or asthma, it is best to avoid the beach. If you have asthma and just can't stay away from the beach during Red Tide, have your rescue inhaler with you at all times. Swimming in the water during a big Red Tide bloom can cause ocular and skin symptoms. If you experience skin or eye irritation, rinse off immediately with freshwater.

To keep an eye on the status of Red Tide, go to

Dr. Mona V. Mangat is a board-certified allergist and immunologist at Bay Area Allergy & Asthma in St. Petersburg. Find her at If you have a question for the doctor, email her at Your question may be answered in a future column.