Bugs, plants, heat, and even water can cause them, so it's important to know how to recognize and treat them.
dr. jennifer lucas is a cleveland clinic dermatologist who says poison ivy is always a summertime concern.
"If you get a mild case of poison ivy, it may be something you're able to manage at home," said Dr. Jennifer Lucas of the Cleveland Clinic. "But if you start to get a spreading of the rash, it's really uncomfortable. you're starting to get blisters, these are times when you should seek medical attention."
Poison ivy and poison oak plants release oil that causes the itchy rash. If you come into contact with it, you can minimize the allergic reaction by scrubbing your skin with soap and water as soon as possible.
Use cold water because hot water may open your pores and spread the oil even more.
If you're bitten by a tick and develop a rash that looks like a "bull's-eye," you may have lyme disease.
That's especially true if the rash expands over a couple of days, in which case - you should see a doctor as soon as possible.
"Swimmer's Itch" is a rash caused by microscopic parasites in a lake, pond, or ocean.
You'll develop small red pimples on your skin, which last about a week and then go away.
Lucas says the summertime heat can also cause a rash.
"The sweat glands, they can crystallize and they can form a rash," she said. "For instance, the time you'll see a heat rash is when you're laying down for a long period of time and sweating on your back.
"You may get a rash on your back because you've accumulated some of the sweat under your skin and it's gotten very irritated."
Lucas says that getting some air on the area and cooling off will be enough to get a heat rash to fade.
She says any rash that continues to spread, or blister, should be seen by a medical professional.