poikiloderma

Your skin is your body's largest organ. It covers the entire outside of your body. There are many ways that your skin protects your body and helps keep you healthy. For example, it:

• Holds body fluids in, which helps prevent you from getting dehydrated
• Keeps out harmful germs, which helps prevent infections
• Helps you feel things like heat, cold, and pain
• Helps control your body temperature
• Makes vitamin D when the sun shines on it
• Shields your body against heat and light

There are many different problems and conditions which can affect your skin. Some of them can cause uncomfortable symptoms, such as itching, burning, redness, and rashes. They might also affect your appearance. Some of the more common skin conditions include:

• Acne, which causes pimples when hair follicles under your skin get clogged up
• Burns
• Cuts and scrapes
• Dandruff, flaking of the skin on your scalp (the top of your head)
• Eczema (atopic dermatitis), which causes inflammation, redness, and irritation of the skin
• Hives, which are red and sometimes itchy bumps on your skin
• Insect bites
• Psoriasis, which causes itchy, scaly red patches
• Skin cancer
• Skin infections

Since your skin protects your body in many ways, it's important to try to keep your skin healthy. For example, you can:

• Wear the right protective equipment, like gloves, long sleeves, knee and elbow pads, or helmets to protect against cuts, bumps and scrapes.
• If you do get a cut or scrape, clean it right away with soap and warm water. Put on a bandage to protect it while it heals.
• When you are spending time outdoors, wear long sleeves and pants and use insect repellant to prevent insect bites.
• Prevent sunburn by covering up and using sunscreen when outdoors.
• Wash your hands often with soap and water.
• When you take a shower or bath, use warm (not hot) water. Use mild cleansers and wash gently (don't scrub).
• Use moisturizers, like lotions, creams, or ointments, to prevent dry skin.

NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases

Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases.

When germs such as bacteria or viruses invade your body, they attack and multiply. This is called an infection. The infection causes the disease that makes you sick. Your immune system protects you from the disease by fighting off the germs.

The immune system has many different parts, including:

• Your skin, which can help prevent germs from getting into the body
• Mucous membranes, which are the moist, inner linings of some organs and body cavities. They make mucus and other substances which can trap and fight germs.
• White blood cells, which fight germs
• Organs and tissues of the lymph system, such as the thymus, spleen, tonsils, lymph nodes, lymph vessels, and bone marrow. They produce, store, and carry white blood cells.

Your immune system defends your body against substances it sees as harmful or foreign. These substances are called antigens. They may be germs such as bacteria and viruses. They might be chemicals or toxins. They could also be cells that are damaged from things like cancer or sunburn.

When your immune system recognizes an antigen, it attacks it. This is called an immune response. Part of this response is to make antibodies. Antibodies are proteins that work to attack, weaken, and destroy antigens. Your body also makes other cells to fight the antigen.

Afterwards, your immune system remembers the antigen. If it sees the antigen again, it can recognize it. It will quickly send out the right antibodies, so in most cases, you don't get sick. This protection against a certain disease is called immunity.

There are three different types of immunity:

• Innate immunity is the protection that you are born with. It is your body's first line of defense. It includes barriers such as the skin and mucous membranes. They keep harmful substances from entering the body. It also includes some cells and chemicals which can attack foreign substances.
• Active immunity, also called adaptive immunity, develops when you are infected with or vaccinated against a foreign substance. Active immunity is usually long-lasting. For many diseases, it can last your entire life.
• Passive immunity happens when you receive antibodies to a disease instead of making them through your own immune system. For example, newborn babies have antibodies from their mothers. People can also get passive immunity through blood products that contain antibodies. This kind of immunity gives you protection right away. But it only lasts a few weeks or months.

Sometimes a person may have an immune response even though there is no real threat. This can lead to problems such as allergies, asthma, and autoimmune diseases. If you have an autoimmune disease, your immune system attacks healthy cells in your body by mistake.

Other immune system problems happen when your immune system does not work correctly. These problems include immunodeficiency diseases. If you have an immunodeficiency disease, you get sick more often. Your infections may last longer and can be more serious and harder to treat. They are often genetic disorders.

There are other diseases that can affect your immune system. For example, HIV is a virus that harms your immune system by destroying your white blood cells. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome). People with AIDS have badly damaged immune systems. They get an increasing number of severe illnesses.

Ultraviolet (UV) rays are an invisible form of radiation. They can pass through your skin and damage your skin cells. Sunburns are a sign of skin damage. Suntans aren't healthy, either. They appear after the sun's rays have already killed some cells and damaged others. UV rays can cause skin damage during any season or at any temperature. They can also cause eye problems, wrinkles, skin spots, and skin cancer.

To protect yourself :

• Stay out of the sun when it is strongest (between 10 a.m. and 2 p.m.)
• Use sunscreen with an SPF of 15 or higher
• Wear protective clothing
• Wear wraparound sunglasses that provide 100% UV ray protection
• Avoid sunlamps and tanning beds

Check your skin regularly for changes in the size, shape, color, or feel of birthmarks, moles, and spots. Such changes are a sign of skin cancer.

Food and Drug Administration