How to Avoid Swimmer’s Itch in Northern Michigan Lakes

Swimmer’s itch is a perennial problem for kids at Northern Michigan beaches, but there are a few simple steps to keep the itching and scratching at bay during a water-logged vacation. Read on to learn how to prevent swimmer’s itch.

What Causes Swimmer’s Itch

The biological mechanisms of swimmer’s itch are quite complex, and the red, raised bumps that characterize it are a side effect of the life cycles of rather resourceful flatworms that inhabit Northern Michigan lakes.

In its simplest terms, swimmer’s itch is a reaction caused by a parasite entering a swimmer’s body. This unwelcome parasite doesn’t live long in the human body: our immune systems recognize the foreign invader and attack it. Just as our bodies react to mosquito bites by inflaming surrounding tissue, our bodies also react to this parasite by rushing resources to the site of entry, leaving itchy, red inflammation. Swimmer’s itch is an uncomfortable by-product of the human immune system—but it’s certainly better than a flatworm swimming around our bodies. The fact that swimmer’s itch is a human response explains why people react differently, as the reaction is determined not by the invading parasite, but by the immune system’s response of each biologically unique human.

The flatworms in question are called schistosomes; the schistosomes that cause swimmer’s itch are among a genus that is also responsible for more serious infectious diseases, but there is no risk of contracting these other illnesses in a Northern Michigan lake. The life cycles of schistosomes require several host species. In lay terms, here’s how their lives typically work: adult worms live inside of birds (mainly ducks) in the blood vessels surrounding the bird’s intestines. The adults lay eggs into the bird’s intestines, where the eggs hatch in the water after being deposited with the host bird’s feces. The hatched larvae—called miracidia—then swim around in search of another host, this time a snail. The larvae enter the snail, develop, multiply and leave the snail in another form—this time cercariae—which then seek out the avian host to repeat the process.  It is during this third stage, when the parasite leaves the snail in search of another bird host, that misguided cercariae run into unsuspecting swimmers and cause swimmer’s itch. Each red bump represents the entry point of one individual cercaria.

How to Prevent Swimmer’s Itch

There’s no cure-all to eliminate swimmer’s itch. The negative symptoms are, ironically, a problem of our own immune system’s making, and short of abstaining from swimming altogether, there’s a risk of getting swimmer’s itch in a Northern Michigan lake.

That being said, here are a few quick tips to keep it at bay:

  • Keep birds away. Even though the organism that causes swimmer’s itch comes from a snail, it’s easier to eliminate other steps in the life cycles of the schistosomes. If there aren’t host birds around your beach, then the parasites in the birds can’t migrate to the snails, and then accidentally to you. Let’s think of their life cycle like a chain of links: it’s much easier to eliminate the bird link than the snail link. And when one link fails, the whole system falls apart, and you can swim in peace. Mergansers are especially prone to becoming hosts, so keep them away at all cost.
  • Towel off after swimming. If you or your kids are swimming at a new beach, it’s best to vigorously towel off after leaving the water.  It’s a little like salt water drying on bare skin: once all the water evaporates, a film of salt is left on the dry skin. This same process applies to swimmer’s itch parasites: they might be swimming around in the beads of water left un-dried on swimmers’ skin, yet only until all that water evaporates will the parasite be able to latch on to the skin and instigate swimmer’s itch. Best to wipe away all the water—and hitchhiking parasites—after exiting the lake.
  • Try creating a waterproof barrier. The parasites are suspended in water, so if swimmers can coat themselves in a waterproof barrier, it’s less likely that the parasites will be able to access the skin, since there’s no physical point of transfer. One simple way to do this is to coat baby oil on the skin. Another way is by purchasing and applying Swimmer’s Itch Guard, which is basically an oil rub with sunscreen.
  • Watch the water. Temperature and wind direction seem to dictate where swimmer’s itch pops up. The water has to be quite warm to sustain the life cycle of swimmer’s itch parasites, and winds that drives surface water to the shore (in other words, a wind coming into the beach) concentrate the organisms near shore—right where the kids are swimming. When the water is a little cooler and the winds are out, you should be safe from swimmer’s itch. Otherwise, exercise caution.
  • Try the Big Lakes. The Great Lakes are typically too tumultuous to sustain snail populations, which means there won’t be swimmer’s itch along wavy sections of Lakes Michigan, Huron and Superior. Watch out for large bays, though: these calmer waters could potentially host swimmer’s itch.

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