Ask Doctor Cory.

Dear Dr. Cory,

I get migraine headaches when I have caffeine or chocolate. What causes this?

Leah Strait Perry, Iowa

Dear Leah:

The exact cause of a migraine headache is unknown. But we do know that migraine headaches occur when arteries in the head tighten, causing a decrease in blood flow, and then expand, causing an increase in blood flow. The swollen arteries may irritate nerve endings and cause pain.

Doctors are not sure why certain foods trigger, or bring on, migraines, but they think there might be a chemical in some foods that causes the blood vessels to widen in the brains of people who have migraines.

Keeping a headache diary can help identify triggers and prevent attacks by noting the situation or the foods eaten just prior to an attack.

Dear Dr. Cory,

What causes nail fungus?

Kimberly Glovers Kincaid, Kansas

Dear Kimberly:

Fungus is usually present on the body. When there is an injury to the nail, it allows tiny fungus spores to enter the nail and live within the nail.

Nail fungus can develop in the fingernails or toenails, but because feet have more injuries, fungal infections are more common on toenails. Fungal infections can be picked up by walking barefoot in public places such as locker rooms, or as a complication of athlete's foot or an infection in the skin surrounding the nail. Keeping feet clean and dry and protecting them with shoes and socks that fit properly may prevent toenail fungus.

A bacterial infection of the nails is more common than a fungal infection and is often mistaken for one. Your physician can tell the difference by doing a culture or looking at nail scrapings under the microscope.

Dear Dr. Cory,

Why do some things taste good to some people and other things taste horrible?

Elyse Hougen Richmond, Texas

Dear Elyse:

Just as we inherit certain features from our parents such as skin, hair, and eye color, we also partly inherit our sense of taste. About a quarter of the population has more taste buds and experiences a stronger sense of taste. Another quarter has less than the normal number of taste buds, so some things may not taste as strong to these people.

Those with more taste buds are more sensitive to a chemical found in certain vegetables like broccoli. To these sensitive people, the taste seems bitter.

Many of us naturally like salty or sweet things, but we are sensitive to bitter tastes. Enjoying bitter drinks such as coffee is a learned or an "acquired" taste.