There are many types of eczema, the most common being atopic dermatitis.
Eczema is not a specific disease, but rather a term that describes a group of inflammatory, rash-like skin conditions.
It's also known as dermatitis (skin inflammation) or atopic eczema ("atopic" means a genetic tendency toward allergic hypersensitivity).
The word "eczema" is often used interchangeably with "atopic dermatitis," which is actually the most common type of eczema.
Eczema is not contagious — it cannot be spread directly between people.
But as with any infection, if the skin affected by eczema becomes infected, it may be possible for that infection to spread to other people.
Types of Eczema
There are multiple types of eczema, including:
Atopic dermatitis This is the most severe and chronic (long-lasting) form of eczema. It's characterized by inflamed skin that may release a clear fluid when scratched (an effect known as weeping).
Allergic contact eczema (dermatitis) This is a condition in which the skin becomes red, itchy, and weepy after touching a substance that the immune system recognizes as foreign or that you've become allergic to, such as poison ivy, nickel, or latex.
Irritant contact eczema This is a localized skin reaction to an irritant, and is often caused by acids, cleaning agents, and certain soaps.
Dyshidrotic eczema This condition is marked by small blisters on the hands and feet.
Seborrheic dermatitis This is a chronic condition in which white or yellow scaly patches of skin develop in oily areas, such as the scalp, face, and ears.
Neurodermatitis (lichen simplex chronicus) This condition is marked by thick, scaly patches of skin on certain parts of the body. It results from frequent rubbing or scratching following a trigger, such as an insect bite.
Nummular eczema This condition is marked by coin-shaped spots of irritation that may be crusted, scaly, or itchy.
Stasis dermatitis This condition is marked by skin irritation and inflammation resulting from blood circulation problems.
What Causes Eczema?
Skin affected by eczema is unable to retain moisture well, possibly due to low production of fats and oils. This causes it to become dry and lose its protective properties.
It's not clear what causes certain people to develop eczema, specifically atopic dermatitis.
Children are more likely to develop eczema if other allergic diseases — such as hay fever and asthma — run in the family, which suggests that there may be a genetic component to the condition.
The symptoms of atopic dermatitis are thought to be the result of an immune system overreaction or dysfunction.
This means that your immune system causes inflammation — a natural process that protects against infection and foreign bodies — even in the absence of harmful substances.
In addition to genetic and immune system factors, environmental factors also play a role in worsening or triggering eczema.
Eczema triggers may include a wide range of irritants, allergens, and other substances, such as:
Soaps, detergents, shampoos, and dishwashing liquids
Bubble bath liquids
Dust or sand
Perfumes and skin care products that contain fragrances or alcohol
Wool or synthetic fabrics
Chemicals, solvents, and mineral oils
Allergenic foods (such as peanuts, soy, and eggs)
A hot or dry climate
High or low humidity
Bacterial, viral, or fungal infections
Stress and hormonal changes can also lead to eczema flare-ups.
Eczema can occur at any age, but it typically begins in infancy and early childhood. It's less common in adults.
Estimates of eczema prevalence vary widely, in part because of different definitions of the condition.
Some sources distinguish between eczema and atopic dermatitis, while others consider them one and the same.
According to the American Academy of Dermatology, 10 to 20 percent of children — and 1 to 3 percent of adults — have atopic dermatitis.
A January 2011 report in the Journal of Investigative Dermatology found that 10.7 percent of children under age 18 in the United States had eczema, or atopic dermatitis.
Furthermore, a study published in November 2013 in the Journal of Allergy and Clinical Immunology found that 10.2 percent of adults in the United States had eczema, and that 3.2 percent had eczema with asthma or hay fever (used as a proxy for atopic dermatitis).
And a June 2007 report in the journal Dermatitis found that 10.7 percent of the population as a whole had eczema, while 6 percent had atopic dermatitis.
Eczema; National Eczema Association.
What Is Atopic Dermatitis? National Institute of Arthritis and Musculoskeletal and Skin Diseases.
Eczema (Atopic Dermatitis); National Institute of Allergy and Infectious Diseases.
J. M. Hanifin and M. L. Reed (2007). "A population-based survey of eczema prevalence in the United States." Dermatitis.
T. E. Shaw, G. P. Currie, C. W. Koudelka, and E. L. Simpson (2011). "Eczema prevalence in the United States: Data from the 2003 National Survey of Children's Health." Journal of Investigative Dermatology.
J. I. Silverberg and J. M. Hanifin (2013). "Adult eczema prevalence and associations with asthma and other health and demographic factors: A US population–based study." Journal of Allergy and Clinical Immunology.