Dog Owners Fact Sheet (HABs)

Protect Your Pets From Harmful Algal Blooms

What are cyanobacteria and harmful algal blooms?

Cyanobacteria (also called blue-green algae) and algae can form harmful algal blooms (HABs) in lakes, ponds, and rivers. Many HABs produce toxins that can harm animals and people. The water may have a scum or be discolored (e.g., green, blue, yellowish, red, or brown). Some blooms may occur along the bottom of the waterbody or become detached and float to the surface or along the shoreline. A visual factsheet is available to help the public identify HABs.1 To learn more, visit the California HABs Portal.2

How can dogs be exposed to HABs?

  • By swimming in lakes, rivers, ponds or any affected water body, drinking the water, or eating algal material. Animals are attracted to the taste and smell of HABs. Dogs lick algae caught in their coat after being in the water. Dogs that scavenge around the shore may ingest drying clumps of algae.
  • By consuming water and algal material from residential pools or decorative ponds.
  • By ingesting health supplements containing blue-green algae, which may unintentionally include HAB toxins.

How can I keep my dog safe from HABs?

  • Do not let your dog drink, wade, or swim in water with a HAB present.
    • Check if a waterbody has a reported bloom by viewing the HAB Report Map, contacting the waterbody manager, and looking for posted advisory signs.2
    • Check for visual signs of a HAB.1
    • If you are still unsure whether a bloom is a HAB, keep pets away from the water.
  • Never let your dog eat scum or algae.
  • Always wash your pets with clean water after water contact.

What are signs of possible cyanobacterial toxin poisoning in dogs?

Animals can experience symptoms within minutes to days following exposure to the toxins. Symptoms include vomiting, diarrhea, weakness, difficulty breathing, seizures, or death. In 2017, there were 18 reported dog deaths from suspected HAB-related exposures in California.

If your pet experiences these symptoms after exposure, contact your veterinarian immediately. A veterinarian fact sheet on diagnosis and potential treatment is available.3 For additional assistance, contact the 24-hour ASPCA Animal Poison Control Center hotline at (888) 426-4435. A $65 consultation fee may be applied.

How can I report a suspected bloom or potential HAB-related illness?

Please report any suspected HAB or potential HAB-related illness using the online report form2, by calling (844) 729-6466, or by emailing

Additional information:

  1. Visual fact sheet.
  2. California HABs portal. HAB report map, advisory signs, online report form, other HAB information.
  3. Veterinarian fact sheet.