What Causes Eczema and What are the Risk Factors?


29 Aug

Eczema Overview

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 eczema are 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 dermatitis 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.

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 themselves.

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.

When Should Someone Seek Medical Care for Eczema?

If twice daily applications of 0.5% or 1% hydrocortisone cream (available without a prescription) are insufficient to control the rash, then the individual should see a physician.

If someone is so uncomfortable that his/her sleep, work, or other daily activities are disrupted, he/she needs a more effective treatment and should see a health care professional.

Generally, eczematous dermatitis is not an emergency and should not be handled in a hospital emergency department. Exceptions include the following:

  • When the skin becomes so irritated that it breaks down and becomes infected; if the rash has become red, hot, and painful; if red streaks are coming from the rash; or if the individual has a fever, an emergency department visit may be necessary if it's not possible to see a health care professional within 24 hours.

Any person with a weakened immune system or certain medical conditions (such as diabetes, on chemotherapy, alcoholism, AIDS, older than 70 years of age) and the above symptoms of infection should go immediately to a hospital emergency department.

What Types of Doctors Treat Eczema?
Most eczema can be managed by primary care physicians (family practice, pediatrics, or internal-medicine doctors). Dermatologists may be consulted when either the diagnosis is in doubt, patients are not responding to treatments that should be working, or higher-risk medications and long-term systemic medications may be needed to get adequate control of the disease.
When seeing a physician, it is important that they know of everything (prescription and over-the-counter drugs, and home remedies) that has been tried and which things helped and which did not. As it is normal for eczema to come and go depending upon many factors, a photo taken to show things at their best or worst may also be useful to the physician.


How Do Health Care Professionals Diagnose Eczema?

A medical professional can usually identify the type of eczematous dermatitis by looking at the rash and asking questions about how it appeared. Samples of scale from the rash may need to be examined microscopically to search for a fungus (ringworm). Occasionally, a portion of skin may be removed (a biopsy) to be examined by a pathologist, but this will not distinguish atopic dermatitis from allergic contact dermatitis. A baby with what appears to be eczema of the palms and soles may have scabies, which may be confirmed with a skin scraping.

Psoriasis will lead to scaly skin but only rarely shows the weeping commonly seen with eczema. Psoriasis also doesn't itch much if at all, and eczema seldom involves the scalp while psoriasis and seborrheic dermatitis often do. While it is possible to have more than one chronic skin condition at a time, it would be unusual to have very active psoriasis and very active atopic dermatitis in the same patient at the same time.

On lighter skin, active eczema is usually red and can leave discoloration as it improves. On dark skin, there may be a mixture of light and dark color changes to the skin during and after a flare. Not enough color (hypopigmentation) is common, but total lack of color (depigmentation) should suggest other conditions, such as vitiligo or discoid lupus.

The three key elements in identifying atopic dermatitis are

  • characteristic appearance and distribution of a chronic rash;
  • severe itching; and
  • atopy, or a personal or family tendency toward asthma and hay fever.


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