The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold.

Skin has three layers:

• The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone.
• The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands.
• The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue.

The skin’s color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis.

Skin Conditions

• Rash: Nearly any change in the skin’s appearance can be called a rash. Most rashes are from simple skin irritation; others result from medical conditions.
• Dermatitis: A general term for inflammation of the skin. Atopic dermatitis (a type of eczema) is the most common form.
• Eczema: Skin inflammation (dermatitis) causing an itchy rash. Most often, it’s due to an overactive immune system.
• Psoriasis: An autoimmune condition that can cause a variety of skin rashes. Silver, scaly plaques on the skin are the most common form.
• Dandruff: A scaly condition of the scalp may be caused by seborrheic dermatitis, psoriasis, or eczema.
• Acne: The most common skin condition, acne affects over 85% of people at some time in life.
• Cellulitis: Inflammation of the dermis and subcutaneous tissues, usually due to an infection. A red, warm, often painful skin rash generally results.
• Skin abscess (boil or furuncle): A localized skin infection creates a collection of pus under the skin. Some abscesses must be opened and drained by a doctor in order to be cured.
• Rosacea: A chronic skin condition causing a red rash on the face. Rosacea may look like acne, and is poorly understood.
• Warts: A virus infects the skin and causes the skin to grow excessively, creating a wart..
• Melanoma: The most dangerous type of skin cancer, melanoma results from sun damage and other causes. A skin biopsy can identify melanoma.
• Basal cell carcinoma: The most common type of skin cancer. Basal cell carcinoma is less dangerous than melanoma because it grows and spreads more slowly.
• Seborrheic keratosis: A benign, often itchy growth that appears like a “stuck-on” wart..
• Actinic keratosis: A crusty or scaly bump that forms on sun-exposed skin. Actinic keratoses can sometimes progress to cancer.
• Squamous cell carcinoma: A common form of skin cancer, squamous cell carcinoma may begin as an ulcer that won’t heal, or an abnormal growth. It usually develops in sun-exposed areas.
• Herpes: The herpes viruses HSV-1 and HSV-2 can cause periodic blisters or skin irritation around the lips or the genitals.
• Hives: Raised, red, itchy patches on the skin that arise suddenly. Hives usually result from an allergic reaction.
• Tineaversicolor: A benign fungal skin infection creates pale areas of low pigmentation on the skin.
• Viral exantham: Many viral infections can cause a red rash affecting large areas of the skin. This is especially common in children.
• Shingles (herpes zoster): Caused by the chickenpox virus, shingles is a painful rash on one side of the body. A new adult vaccine can prevent shingles in most people.
• Scabies: Tiny mites that burrow into the skin cause scabies. An intensely itchy rash in the webs of fingers, wrists, elbows, and buttocks is typical of scabies.
• Ringworm: A fungal skin infection (also called tinea). The characteristic rings it creates are not due to worms.

1) Eczema

The term eczema is derived from the Greek, meaning "to boil out." The name is particularly apt since to ancient medical practitioners it may have appeared that the skin was "boiling." Today the usage is rather imprecise since this term is frequently used to describe any sort of dermatitis (inflammatory skin condition). But not all dermatitis is eczematous. All eczematous dermatitis, whether due to a familial atopic dermatitis or an acquired allergic contact dermatitis, has a similar appearance. Acute lesions are composed of many small fluid-filled structures called vesicles that usually reside on red, swollen skin. When these vesicles break, clear or yellowish fluid leaks out, causing characteristic weeping and oozing. When the fluid dries, it produces a thin crust which may mimic impetigo. In older lesions, these vesicles may be harder to appreciate, but an examination of the tissue under the microscope will reveal their presence.

Eczematous dermatitis has many causes. One of the most common is a condition called atopic dermatitis. Often those using the term eczemaare referring to atopic dermatitis. Although atopy refers to a lifelong inherited (genetic) predisposition to inhalant allergies such as asthma and allergic rhinitis (hay fever), atopic dermatitis is not known at this time to be a pure allergic disease. Atopic patients are likely to have asthma, hay fever, and dermatitis. Atopy is a very common condition, and it affects all races and ages, including infants. About 1%-2% of adults have the skin rash, and it is even more common in children. Most affected individuals have their first episode before 5 years of age. For most, the dermatitis will improve with time. For an unlucky few, atopic dermatitis is a chronic, recurrent disorder.

Other eczematous dermatoses include, but are not limited to, allergic contact dermatitis (cell-mediated allergy to a common substance such as poison oak or nickel), irritant dermatitis (from excessive contact with a harsh chemical substance), fungal infections (ringworm), scabies infestations, stasis dermatitis, very dry skin (asteatosis), pompholyx (dyshidrosis), nummular dermatitis, and seborrheic dermatitis. The differentiation among these conditions is often difficult and time consuming. In addition, it is not uncommon for atopic dermatitis to coexist with another eczematous dermatitis.

What Are Causes and Risk Factors of Eczema?

It is generally agreed that the tendency to atopy is inherited. For the purposes of this discussion, the term eczema and atopic dermatitis will be synonymous. Individuals with atopic dermatitis have a variety of abnormal immunologic findings, like elevated IgE antibody (immunoglobulin E) levels and defective cell-mediated immunity, which causes difficulty in fighting off certain viral, bacterial, and fungal infections. Despite a susceptibility to certain infections, eczema is not itself contagious in any way.

Like most other noninfectious diseases, atopic skin disease can be triggered by environmental factors. One of the hallmarks of atopic dermatitis is excessive skin dryness, which seems to be due a lack of certain skin proteins called filaggrins. Any factor that promotes dryness is likely to worsen atopic dermatitis. A very dry sleeping environment may be improved with a bedroom or house humidifier.

Common triggers of atopic dermatitis include the following:

• Harsh soaps and detergents
• Overwashing of skin
• Solvents
• Low humidity
• Lotions
• Rough wool clothing
• Sweating
• Occlusive rubber or plastic gloves
• Rubbing
• Staphylococcus bacteria
• Repeated wetting and drying of the skin (as occurs with food handling or other professions requiring frequent hand washing)
• While food allergies are implicated as triggers in some patients, there is no dietary restriction or recommendation which is universally helpful.
• Eczema may be worsened by the development of additional problems such as allergic contact dermatitis, which may occur as a reaction to preservatives and active ingredients in moisturizers, and even as a reaction to the topical corticosteroids used.

What Are Symptoms and Signs of Eczema

Medical professionals sometimes refer to eczema as "the itch that rashes."

• Usually, the first symptom of eczema is intense itching.
• The rash appears later and is red and has bumps of different sizes.
• The rash itches and may burn, especially in thin skin like the eyelids.
• If it is scratched, it may ooze and become crusty.
• In adults, chronic rubbing produces thickened plaques of skin.
• Having one or more round areas is referred to as nummular (coin shaped) eczema and may be confused with fungal infections.
• Some people develop red bumps or clear fluid-filled bumps that look "bubbly" and, when scratched, add wetness to the overall appearance. This type of eczema is especially common on the sides of the finger in dyshidrotic eczema and also goes by the name pompholyx.
• Painful cracks in the skin can develop over time.
• Although the rash can be located anywhere on the body, in adults and older children, it is most often found on the neck, flexures of the arms (opposite the elbow), and flexures of legs (opposite the knee). Infants may exhibit the rash on the torso and face. It usually first appears in areas where the child can rub against sheets, since they may not have the coordination to precisely scratch yet. As the child begins to crawl, the rash involves the skin of the elbows and knees. The diaper area is often spared.
• The scalp is rarely involved.
• While the skin behind the ear may be involved, the outer ear itself is usually spared.
• Eyelids are often puffy, red, and itchy.
• The itching may be so intense that it interferes with sleep.
• While classic eczema and psoriasis are distinctly different and seldom coexist, both conditions may have severe erythrodermic (red skin) forms in which the patient has inflammation of most of the skin surface area.
• Asteatotic eczema is a term often applied to describe patients who have thin, dried, cracked-appearing skin, usually especially bad on the lower legs.
• Significant involvement of the palms and soles of the feet is not usual and may suggest a different condition such as fungal infection, scabies infestation, or allergic contact dermatitis

2) PSORIASIS

What Is Psoriasis?

Psoriasis causes red, scaly patches to appear on the skin. It can look like a rash, so you may worry that you could get it from someone else or pass it to others. But rest easy: It's not contagious. You cannot catch the disease by touching someone who has it.

What Causes Psoriasis?

Though psoriasis symptoms show up on the skin, the condition is actually a problem with the immune system, called an autoimmune disease. It means the body’s defenses overreact or react at the wrong times, which affects the body inside and out.

When people have psoriasis, their immune systems cause skin cells to grow much faster than normal. They pile up too quickly and form thick, scaly lesions.

There are several different kinds of the disease, but the most common is plaque psoriasis. Lesions often appear on the knees, elbows, or scalp, although they can be anywhere on the body. These patches can feel swollen, itchy, and sore, and may crack and bleed. Other types of the condition may cause small red spots, pus-filled bumps, or red scaling patches all over

Unpredictable and irritating, psoriasis is one of the most baffling and persistent of skindisorders. It's characterized by skin cells that multiply up to 10 times faster than normal. As underlying cells reach the skin's surface and die, their sheer volume causes raised, red plaques covered with white scales. Psoriasis typically occurs on the knees, elbows, and scalp, and it can also affect the torso, palms, and soles of the feet.

The symptoms of psoriasis vary depending on the type you have. Some common symptoms for plaque psoriasis -- the most common variety of the condition -- include

• Plaques of red skin, often covered with loose, silver-colored scales; these lesions may be itchy and painful, and they sometimes crack and bleed. In severe cases, the plaques of irritated skin will grow and merge into one another, covering large areas.
• Disorders of the fingernails and toenails, including discoloration and pitting of the nails; the nails may also begin to crumble or detach from the nail bed.
• Plaques of scales or crust on the scalp

Psoriasis can also be associated with psoriatic arthritis, which leads to pain and swelling in the joints. The National Psoriasis Foundation estimates that between 10% to 30% of people with psoriasis also have psoriatic arthritis

Other forms of psoriasis include:

Pustular psoriasis, characterized by red and scaly skin on the palms of the hands and/or feet with tiny pustules

Guttate psoriasis, which often starts in childhood or young adulthood, is characterized by small, red spots, mainly on the torso and limbs. Triggers may be respiratory infections, strep throat, tonsillitis, stress, injury to the skin, and use of anti-malarial and beta-blocker medications.

Inverse psoriasis, characterized by bright red, shiny lesions that appear in skin folds, such as the armpits, groin area, and under the breasts

Erythrodermic psoriasis, characterized by periodic, fiery redness of the skin and shedding of scales in sheets; this form of psoriasis, triggered by withdrawal from a systemic psoriasis treatment, severe sunburn, infection, and certain medications, requires immediate medical treatment, because it can lead to severe illness.

People who suffer from psoriasis know that this uncomfortable and at times disfiguring skin disease can be difficult and frustrating to treat. The condition comes and goes in cycles of remissions and flare-ups over a lifetime. While there are medications and other therapies that can help to clear up the patches of red, scaly, thickened skin that are the hallmark of psoriasis, there is no cure.

What Causes Psoriasis?

A variety of factors -- ranging from emotional stress and trauma to streptococcal infection -- can cause an episode of psoriasis. Recent research indicates that some abnormality in the immune system is the key cause of psoriasis. As many as 80% of people having flare-ups report a recent emotional trauma, such as a new job or the death of a loved one. Most doctors believe such external stressors serve as triggers for an inherited defect in immune function.

Injured skin and certain drugs can aggravate psoriasis, including certain types of blood pressure medications (like beta-blockers), the anti-malarial medication hydroxychloroquine, and ibuprofen (Advil, Motrin, etc.).

Psoriasis tends to run in families, but it may be skip generations; a grandfather and his grandson may be affected, but the child's mother never develops the disease. Although psoriasis may be stressful and embarrassing, most outbreaks are relatively harmless. With appropriate treatment, symptoms generally subside within a few months.

3) VITILIGO

Vitiligo is a condition in which white patches develop on the skin. Any location on the body can be affected, and most people with vitiligo have white patches on many areas.

Causes

The skin doesn't have its characteristic color because it has lost its melanin. For some reason, the pigment-forming cells known as melanocytes have been destroyed.

We don't know exactly why this happens. It might be an autoimmune condition, where your body's defenses turn on your own cells instead of attacking invading germs.

Although vitiligo affects all races equally, it's more noticeable in dark-skinned people.

Who Is Likely to Get It?

Up to 2% of the population and an estimated 2 to 5 million Americans have the condition. It doesn't matter if you're a man or a woman.

In most cases, it develops early in life, between ages 10 and 30. It will almost always show up before age 40.

Vitiligo may run in families. You're more likely to get it when someone else in your family has it, too, or when people in your family get gray hairprematurely.

Autoimmune diseases, such as autoimmune thyroid disease (Hashimoto's thyroiditis) or type 1 diabetes, can also raise your odds.

Symptoms

You'll often lose pigment quickly on several areas of your skin. After the white patches appear, they may stay the same for a while, but later on, they might get bigger. You may have cycles of pigment loss and stability.

Vitiligo commonly affects body folds (such as armpits), places that have been injured in the past, and areas exposed to sun, around moles, or around body openings. It can also affect eyelids and hair.

4) ITCHING

Itch facts

• The medical term for itching is pruritus.
• Infections, bites and stings, infestations, chronic diseases, atopic dermatitis, psoriasis, allergicreactions, sun exposure, and dry skin are among the numerous and common causes of itching.
• Some cases of itching will respond to corticosteroid medications.
• It is important to avoid scratching when possible to prevent worsening of the condition and disruption of the skin that could lead to bacterial infection.
• If itching persists, worsens, or is associated with skin lesions, consulting a health-care professional is advisable.

What is an itch?

Itch is an irritation in the skin that elicits an urge to scratch. Itches are a problem that everyone experiences, and the symptom can be localized (limited to one area of the body) or generalized (occurring all over the body or in several different areas). Sometimes, depending upon the underlying cause, itching may be worse at night. In medical terminology, itching is known as pruritus.

Generalized itch that occurs all over the body is often more difficult to treat than localized itch. Itches can also occur with or without skin lesions (bumps, blisters, rash, redness, or abnormalities that can be seen on the skin). An itch that is accompanied by a visible skin abnormality should be evaluated by a physician only.

What are associated symptoms and signs of itching (pruritus)?

Depending upon the underlying cause, itching may be associated with other symptoms and signs. Most commonly, these associated findings include skin lesions such as rash, blisters, bumps, or redness of the affected area. Dryness of the skin is a common cause of itch. Itching of skin can lead to tears in the skin (excoriations) from scratching. Less commonly, generalized itching all over the body can be a sign of chronic medical conditions such as liver disease. In these situations, there may be no changes to the appearance of the skin.

How to diagnose itching?

As with any condition, a careful medical history and physical examination will suggest to your health care provider the particular diagnostic tests that may be needed to learn the cause of itching. Some common causes like dry skin or sunburn may be obvious, while causes such as chronic systemic diseases or conditions may require blood or imaging tests to identify. If a skin condition is responsible for the itch, sometimes a scraping or biopsy may be performed to identify the condition. Nevertheless, many common rashes and skin ailments have a characteristic symptom or appearance that may suggest the correct diagnosis.

5) SUNBURN

Sunburns all start with melanin and UV rays. The UV rays found in sunlight and tanning beds damage the skin by damaging the DNA inside of cells. Once the DNA is damaged, the cell usually dies. Melanin is the skin's defense against this damage.

When the skin is exposed to the sun, it makes more melanin to protect the skin's lower layers from damage. As the skin becomes damaged, it produces even more melanin. The extra melanin causes some people to become a darker color, or tan. Other people turn red, which is a sign of a sunburn. The redness of a sunburn comes from the body flooding the area with blood to treat the damage and from inflammation of the skin.

To protect the skin, the melanin absorbs the UV light. Then, it disperses it as heat.

Melanin is also what makes people have light or dark skin. People with light skin have very little melanin while people with dark skin have a lot of melanin. How long a person spends in the sun, combined with their skin type, determines if and when a person burns.

Symptoms

Symptoms of a sunburn, which typically start a few hours after exposure, include hot, pink or red skin that can be tender to the touch. Some swelling may also occur. In severe cases, the person may experience headache, fever, fatigue and chills.

In second-degree burns, the skin may form liquid-filled boils as a way to cool down the area. "If the blisters cover a large area, such as the entire back, or you have chill.

Symptoms of sunburn can last for days as the skin repairs. The worse the burn, the longer the healing will take. Typically, a sign that the end is near is the damaged areas peeling and falling off.