In response to reports of algae blooms and swimmer’s itch at Lake Tye, the City of Monroe is coordinating water quality testing and has notified the Snohomish Health Department. The city posted cautionary signage at the lake per standard protocol. Cercarial dermatitis, also known as “swimmer’s itch”, is a short-term allergic reaction on the skin that can be caused by algal blooms found in lakes during warm weather. The algal blooms (also known as cyanobacteria) occur when lake temperatures rise and in addition to being a skin irritant, can also be toxic to drink for both humans and pets.
Testing will be conducted at Lake Tye this Monday to monitor the algae levels; it is recommended to refrain from swimming in the lake or letting pets drink the water until the algal toxicity levels are measured.
If high levels of toxins are identified during testing, alerts will be posted on this page and the lake public access sites. Until algal toxicity levels are known, it is recommended to exercise caution. If you see an algal bloom in other city water, please report it to the stormwater compliance coordinator Vince Bertrand. Additional information can also be found at: https://www.cdc.gov/parasites/swimmersitch/.
When in doubt – stay out.
1. Swimmers itch – this can cause raised itchy red bumps that appear within hours of swimming. It is typically short term, and symptoms usually last no longer than a week. I might be suspicious of this particularly if there are a lot of geese or ducks in the area. It is caused by a waterborne parasite, the free-swimming stage of a flatworm. The life cycle is a bit complicated, but involves waterfowl and snails. Humans cannot be hosts to the parasites, but can accidentally pick up the parasites when swimming. When the swimmer gets out of the water, the parasites burrow into the swimmer’s skin and then die, causing the allergic reaction in the skin and the subsequent itchy bumps. There really is no good way to treat swimmer’s itch, but it can be minimized by toweling off or showering immediately after lake use.
We do not do any testing for swimmer’s itch, and I don’t think the health district does either. The Health District has occasionally put up signs warning of the presence of swimmer’s itch if they get enough complaints at a particular lake, but I have not seen those in quite a few years. A few resources regarding swimmers itch are:
2. Blue green or “toxic” algae - . Another possible culprit for skin rashes from swimming in lakes may be blue-green algae or cyanobacteria. Most species of blue-green algae have the potential to produce a dermatoxin or skin irritant. If there is a high concentration of blue-green algae and/or algae scum, it is possible that this can cause skin irritation. However, we have not had reports from citizens or our volunteer lake monitor of any blue-green algae blooms. It appears like blue or green paint floating on the surface or sometimes as clumps floating in the water. It would break apart easily if the water is disturbed (as opposed to filamentous algae which is stringy and not harmful)
3. Sensitivity to a particular plant or algae – sometimes people may just have a particular sensitivity to a plant along the shoreline or potentially an algae (other than blue-green) that happens to be at high level at that time. An example is yellow flag iris. I’ve pasted in a picture below. These plants are a noxious weed that is very common around Flowing Lake. Some people are very sensitive to the resin in the plant leaves when they come in contact with the resin (usually more from pulling or cutting them). This would likely be restricted to just the area that was exposed.