Key points
- Harmful algal blooms can cause mild to life-threatening illnesses.
- Illnesses depend on the toxin, exposure, and individual factors.
- Patients can have dermal, gastrointestinal, cardiovascular, neurologic, hepatic, respiratory, or other symptoms.
![Woman with stomach ache Woman sitting on a couch holding her stomach with her eyes closed and a pained look on her face](/harmful-algal-blooms/media/images/2024/04/symptoms-woman-w-stomach-cramps-GettyImages-1275799083-476px.jpg)
Signs and symptoms
Many factors determine whether a person will develop signs or symptoms from exposure to a harmful algal bloom, including:
- Toxin type
- Toxin concentration
- Duration of exposure
- Route of exposure
- Other conditions or diseases the person has
These factors also influence the severity of signs or symptoms.
Symptoms vary by toxin
Harmful algal blooms that grow in fresh water make different toxins and often cause different symptoms than those in salt water.
Some of the more common symptoms caused by a range of harmful algal bloom toxins include:
- Vomiting
- Diarrhea
- Headache
- Rash
- Cough
In more severe cases, certain toxins can cause life-threatening signs or symptoms including:
- Respiratory paralysis
- Coma
- Liver damage
Symptoms vary by exposure route
Skin or eye contact with contaminated water can cause irritation, such as rash or conjunctivitis.
Inhaling aerosolized toxins can cause respiratory irritation, such as cough or shortness of breath.
Ingesting contaminated water or food can cause a wide range of gastrointestinal, cardiovascular, neurologic, hepatic, respiratory, or other signs and symptoms.
Long-term effects
The long-term health effects of harmful algal blooms remain unclear. Researchers are still learning about these effects.