Ask doctor Cory.

Dear Dr. Cory:

Yesterday I had a ton of freckles. They were all over my face. Today I barely have any. What happened?

Nikki

Stevensville, Montana

Dear Nikki:

Freckles are often found on skin that is exposed to the sun, especially on those who have fair skin or a family history of freckles. Freckles tend to get darker or more noticeable after being in the sun.

You can get more freckles as you grow, depending on your skin type and how well you protect your skin from the sun. Often they're an early warning sign that you're getting too much sun.

Be sure that you are using a waterproof, broad spectrum sunscreen that protects against both ultraviolet A (UVA) and ultraviolet B (UVB) rays, with a sun protection factor (SPF) of 15 or more.

If you are, and are still getting freckles, try using a SPF 30 sunscreen or a sunblock. Apply it 30 minutes before going out in the sun in order for your skin to have time to absorb it.

Reapply it every two hours or immediately after swimming or strenuous activities. Sunscreen should be applied every day all over the body, including beneath clothing. Clothing provides some protection, especially tightly woven clothing, but sunscreen is still needed.

Tanning Booth Blues

You receive 80 percent of your lifetime sun exposure by the time you are 18. Suntanning and indoor tanning greatly increase the risk for skin cancer.

They also lead to early wrinkling, sagging, and discoloration of the skin. Teens who think that tans make them look good now will be in for a big surprise when, as an adult, they look old way before their time.

Dear Dr. Cory:

Why do we get brain-freezes after eating something cold?

Jocelyn

Cary, Illinois

Dear Jocelyn:

Doctors who specialize in the care of the brain and nervous system think this kind of headache might be related to the effect of cold on the nerves of the roof of the mouth.

Here's how: Ordinarily, blood vessels react to cold by narrowing, which lets less blood come to the surface and limits heat loss. This narrowing of blood vessels in the head could be causing the pain of "brain freeze," which usually only lasts a couple of minutes.

To avoid this unpleasant feeling, try keeping cold foods from touching the roof of your mouth.

Dear Dr. Cory:

Sometimes I get this pain in my chest. Is this something dangerous?

Edwina

Plantation, Florida

Dear Edwina:

Sharp chest pains in children your age can be from muscle cramps.

These sometimes occur when you are nervous and don't breathe very deeply. Or they can occur after hard exercise or work.

You can also get sore muscles in the chest, upper abdomen, and diaphragm (DIE-uh-fram)--the large muscle beneath your lungs that aids in breathing--from coughing, especially a hacking kind of cough.

Chest pain in children is rarely caused by heart disease. But if the pain continues, is always brought on by exercise, stops you from doing things, or is frequent, please let your doctor know about it.

Sincerely,

Cory SerVaas, M.D.