Blue-green algae symptoms in people

Common symptoms

The CDC lists these as the common symptoms of contact with harmful algae or their toxins:

• Stomach pain, often with vomiting or diarrhoea after swallowing water
• A skin rash, itching or hives
• Headache
• Coughing, a sore throat or nose irritation, especially after breathing in spray
• Watery or irritated eyes

You can be exposed by swallowing water, by touching it, or by breathing in tiny droplets during activities like water-skiing or jet-skiing. What you feel depends on how you were exposed, for how long, which toxin was present and how much of it.

Serious illness

In rare cases algal toxins cause serious illness, including liver damage, seizures and an irregular heartbeat. According to the CDC, serious illness is most often linked to swallowing water or eating seafood that contains certain toxins. Get emergency help straight away for seizures, trouble breathing, confusion, yellowing skin or eyes, or severe vomiting.

Who is most at risk

Children are at higher risk because they are smaller, play where scum collects at the water's edge and are more likely to swallow water. People who drink untreated lake water, or who take part in activities that send spray into the air, have more exposure. Dogs are at even greater risk than people: see toxic algae and dogs.

What to do if you think you've been exposed

• Rinse off with clean tap water as soon as you can, including your hair and swimwear.
• Call Poison Control on 1-800-222-1222 for advice, any time of day.
• See a doctor if you have symptoms. Tell them which lake, when, and what the water looked like.
• Don't drink untreated lake water, even after boiling it. Boiling doesn't destroy algal toxins.

Reporting an illness or a bloom

The CDC asks people to report suspected algae-related illnesses to their local or state health department, which helps states find blooms and warn others. The state pages on this site link to each state's official data and live maps:

• California: California State Water Resources Control Board
• Florida: Florida Department of Environmental Protection (DEP)
• Kansas: Kansas Department of Health and Environment (KDHE)
• New York: New York State Department of Environmental Conservation (DEC)
• Oregon: Oregon Health Authority (OHA)

Questions

How long after swimming do blue-green algae symptoms start?

It depends on the toxin, how you were exposed and how much water you swallowed or touched. Some people notice skin or eye irritation soon after swimming, while stomach symptoms can take longer. If you feel unwell after contact with lake water, contact a doctor and mention the water.

Can blue-green algae make you seriously ill?

Most people have mild symptoms such as a rash or stomach upset. Serious illness, including liver damage, seizures and an irregular heartbeat, is rare and is most often linked to swallowing water or eating seafood with certain toxins.

Is there a test for blue-green algae poisoning?

There is no simple routine test. Doctors usually diagnose it from your symptoms and your contact with a bloom, and treat the symptoms. Telling them where and when you were in the water helps.

Can you get sick from eating fish from a lake with algae?

Toxins can build up in fish, especially in the liver and guts. Health agencies advise not eating fish caught in an active bloom, or at least removing the guts and liver and rinsing fillets in clean water.

Does boiling lake water make it safe?

No. Boiling doesn't destroy algal toxins. Never drink untreated lake water, especially during a bloom.