Clinical trials are research studies that test how well new medical approaches work in people. Each study answers scientific questions and tries to find better ways to prevent, screen for, diagnose, or treat a disease. Clinical trials may also compare a new treatment to a treatment that is already available.

Every clinical trial has a protocol, or action plan, for conducting the trial. The plan describes what will be done in the study, how it will be conducted, and why each part of the study is necessary. Each study has its own rules about who can take part. Some studies need volunteers with a certain disease. Some need healthy people. Others want just men or just women.

An Institutional Review Board (IRB) reviews, monitors, and approves many clinical trials. It is an independent committee of physicians, statisticians, and members of the community. Its role is to:

• Make sure that the study is ethical
• Protect the rights and welfare of the participants
• Make sure that the risks are reasonable when compared to the potential benefits

In the United States, a clinical trial must have an IRB if it is studying a drug, biological product, or medical device that the Food and Drug Administration (FDA) regulates, or it is funded or carried out by the federal government.

NIH: National Institutes of Health

Cosmetics are products you apply to your body to clean it, make it more attractive, or change the way it looks. They include:

• Hair dyes
• Makeup
• Perfumes
• Skin-care creams

Cosmetics that treat or prevent diseases are also drugs. Products such as dandruff shampoo, fluoride toothpaste, and antiperspirant deodorant are both cosmetics and drugs. A good way to tell if you're buying a cosmetic that is also a drug is to see if the first ingredient listed is an "active ingredient." The active ingredient is the chemical that makes the product effective. The manufacturer must have proof that it's safe for its intended use.

Cosmetics can cause allergic reactions. The first sign is often red and irritated skin. Fragrances and preservatives are the most common causes of skin problems.

To find out all the ingredients in a cosmetic you use, check the container. Manufacturers are required to list them. Labels such as "natural" and "hypoallergenic" have no official meaning. Companies can use them to mean whatever they want.

Food and Drug Administration

Computed tomography (CT) is a type of medical imaging test that uses special x-ray equipment to make detailed pictures of the inside of your body.

A CT scan produces cross-sectional pictures, which are like slices of the body. These images show the size and structure of organs, bones, and other tissues. CT images can also be combined to create 3-dimensional (3D) views.

Health care providers use CT scans to diagnose, treat, and monitor many health conditions.

Your provider may suggest a CT scan for many reasons, including:

• Fractures (broken bones)
• Cancer
• Tumors or masses
• Blood clots
• Signs of heart disease
• Spinal conditions
• Lung disease

CT scans may also be used to find the best place to perform a biopsy or help guide certain treatments. They may also be used to check for internal bleeding or injury after trauma or to evaluate the brain for certain conditions.

You may be asked not to eat or drink for a few hours before the scan. Ask your provider if there are any special instructions to follow.

For some CT scans, you may receive a contrast material. Contrast helps certain parts of the body show up more clearly on the images. Depending on what area is being examined, contrast material might be given as:

• A liquid to swallow
• A shot (injection)
• An enema (placed into the rectum)

CT scans use ionizing radiation at levels higher than a standard x-ray, but the amount is kept as low as possible. Always tell your provider if you are pregnant or think you may be pregnant.

You may be asked to change clothes and remove jewelry or other items that could interfere with the scan.

During the scan, you lie still on a table. The table slowly passes through the center of a large donut-shaped machine. The x-ray tube rotates around your body to create images.

You may hear whirring sounds during the scan. You may be asked to hold your breath for short periods. The test is painless.

The scan usually takes a few minutes, but some may last up to 30 minutes, depending on the area being scanned.

Most people can return to normal activities right away. If you were given a contrast material, drinking fluids can help your body clear it.

A specialist called a radiologist reviews the images and shares the results with your provider.

NIH: National Cancer Institute

You lose up to 100 hairs from your scalp every day. That's normal, and in most people, those hairs grow back. But many men -- and some women -- lose hair as they grow older. You can also lose your hair if you have certain diseases, such as thyroid problems, diabetes, or lupus. If you take certain medicines or have chemotherapy for cancer, you may also lose your hair. Other causes are stress, a low protein diet, a family history, or poor nutrition.

Treatment for hair loss depends on the cause. In some cases, treating the underlying cause will correct the problem. Other treatments include medicines and hair restoration.

Health disparities are health differences between different groups of people. These health differences may include:

• How many people get certain diseases
• How severe the diseases are
• How many people have complications because of the diseases
• How many people die from a disease
• Whether people can get health care
• How many people get screened for a disease

These groups of people may be based on:

• Race
• Ethnicity
• Immigrant status
• Disability
• Sex or gender
• Sexual orientation
• Geography
• Income
• Level of education

NIH: National Institute on Minority Health and Health Disparities