Symptoms and Signs of Seaweed Irritation

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 9/30/2021

Doctor's Notes on Seaweed Irritation

Seaweed such as algae and coelenterates are found worldwide in salt water and fresh water and can cause skin irritation. A seaweed rash usually occurs when swimmers have direct contact with Lyngbya majuscule. This seaweed is found worldwide and resembles dark matted clumps of hair (gray, greenish-black, reddish and yellow colors) and produces two toxins that cause skin irritation. It can cause a rash when it gets under bathing suits or in areas where skin-to-skin contact occurs such as under the breasts or in the groin region. It is also common to see this rash along the waistband of bathing suits. 

Symptoms of seaweed irritation include

  • skin itching,
  • burning sensation,
  • skin redness, and in some people,
  • blisters can develop or swelling may occur.

What Is the Treatment for Seaweed Irritation?

Seaweed irritation usually only causes mild to moderate symptoms. If you have contact with seaweed that causes irritation, it is best to rinse your skin and bathing suit right away with soap and fresh water.

If a rash develops in the area of the seaweed exposure, home self-care with over-the-counter (OTC) treatments such as the following can be used:

If you develop severe symptoms of seaweed irritation such as shortness of breath, hives, eye irritation, or fever, seek medical care right away.

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Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.