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Why do we have germs on our hands? – Prince, 12, Georgia

Dear Prince,

Germs are tiny organisms—also called microbes. They’re so small you have to zoom in with a microscope to see them. They can be bacteria, viruses, fungi or other teeny things. Some microbes make us sick. Some don’t bother us at all. Some help us out.

I talked about all that with my friend Eric Lofgren. He studies infectious disease at Washington State University.

He said there are two main reasons we have germs on our skin. We pick up some microbes from the environment. Some live on our skin all the time.

“The world is full of microbes,” Lofgren said. “They’re very … » More …

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Why do we get rashes on our skin? – Claire, 9, Virginia

Dear Claire,

I’ve been allergic to fleas ever since I was a kitten. Flea bites give me an itchy, red rash.

I talked about why that happens with my friend Bevan Briggs. He’s a nurse practitioner and professor at Washington State University. Nurse practitioners are nurses with advanced training. They diagnose illnesses, order tests and prescribe medicine.

Briggs told me that often rashes happen when the immune system gets turned on. The immune system is the body’s defense system.

“It's the way our body tries to protect us from germs and poisons,” he said. “Rashes happen because your immune system identifies something as foreign—either an infective agent or some kind of toxin.”

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Why do you get acne? – Joey, 12, Illinois

Dear Joey,

Whether we call them pimples, spots or zits, acne is something most people experience. As many as 95% of people have some acne sometime. That’s nearly everybody.

I talked about acne with my friend Sarah Fincham. She has a clinical doctorate in nursing. She’s a nurse and a professor in the College of Nursing at Washington State University.

If you look at your skin, you’ll see tiny openings called pores. These pores connect to oil-producing glands under our skin. They’re called sebaceous glands, and the oil they make is called sebum.

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Dr. Universe: Why do people have different fingerprints? - Mary, 12, South Carolina

Dear Mary,

Did you know even identical twins have different fingerprints? It can be hard to tell twins apart, but a close look at their fingertips can reveal who’s who. The reason lies partly in their genes, but mostly from the unique way everyone’s skin grows before birth.

That’s what I learned from my friend David M. Conley, a professor at Washington State University’s Elson S. Floyd College of Medicine.

“The reason fingerprints are unique is the same reason individual humans are unique,” Conley said. “Variation is the norm, not the exception.”

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