Swimmers using southeast Idaho beaches have been complaining this week about skin rashes.
It's called swimmer's itch, and the Southeastern Idaho Public Health District said it's caused by an allergic reaction to microscopic parasites.
Environmental Health Director Steve Pew said the parasites are found mostly in shallow water, and they are carried by waterfowl and snails.
The parasites can burrow into your skin, and that's what causes the reaction.
Most cases do not require medical attention, and some people never see symptoms.
But when Gillian Cook of Blackfoot went on an outing with family and friends to swim at Jensen's Grove in Blackfoot, after about an hour and a half, the children in the group were reacting to something in the water.
"(They were) complaining of itching horribly, uncontrollably. Half of them were crying because they could not get any relief," Cook wrote in an email to Local News 8 and Eyewitness News. "A couple hours after leaving and doing oatmeal baths and Benadryl for the itch, we noticed little black spots on a few of them with red lines coming from them. When they were squeezed, a black inch-long worm came shooting out."
If you're swimming on an outdoor beach like Jensen's Grove, shower immediately and briskly dry off with a towel as soon as you get out of the water. The health district also suggests not to feed waterfowl in areas where people swim.
For more information on this and other public health issues, visit the SIPH website at http://siphidaho.org.