Eczema and dermatitis are common conditions that cause skin inflammation. This inflammation can affect people of all ages and may result in redness, bumps, dryness, cracking, or a scaly texture. Often, skin affected by eczema and dermatitis is so intensely itchy that people may not be able to resist scratching, especially at night.
Eczema and dermatitis are neither contagious nor life threatening. But skin inflammation may cause physical and social discomfort. Rashes may develop anywhere on the body but can be especially uncomfortable when they appear on the face and hands.
Understanding the types of eczema and dermatitis can be difficult; sometimes, the terms “eczema” and “dermatitis” are used interchangeably in casual conversation. Our dermatologists differentiate between them because treatments may differ.
Atopic dermatitis is often called “eczema” and is sometimes also called “atopic eczema.”
Atopic dermatitis tends to run in families, and it’s more often seen in babies and children under the age of five years than in people in other age groups. Atopic dermatitis can appear at any age but often appears before a child is a year old.
The most common symptom of atopic dermatitis is an itchy rash in the skin folds of the arms, legs, and face. Sometimes, itching occurs before redness appears; that’s because the immune system releases substances under the skin that cause itching before the rash is evident.
Atopic dermatitis may also appear before or at the same time as hay fever, food allergy, or asthma—the term “atopic” indicates a tendency for these allergic conditions to develop together. These other medical conditions are not caused by atopic dermatitis, nor do they cause it, but doctors have noted that they often develop after skin irritation forms. The reasons for this are unclear and are being researched.
In infants, rashes may appear as red, scaly patches. They frequently develop on the face, especially the cheeks, but can emerge anywhere on the body. In children, the inflammation tends to appear in the crooks of elbows, behind the knees, and on the wrists and ankles. Atopic dermatitis rarely develops for the first time in adults, but many children who have it experience symptoms into adulthood. When adults develop atopic dermatitis, the itchy rashes can appear anywhere on the body.
Contact dermatitis occurs when your skin comes into contact with an allergen or irritant, and the body’s immune system responds with inflammation, which leads to redness, swelling, itching, cracking, and sometimes blistering. There are two distinct types of contact dermatitis: allergic dermatitis and irritant dermatitis.
Allergic dermatitis occurs when your skin has a physical reaction after coming into contact with a substance to which your body is allergic. There are thousands of possible causes of an allergic reaction, including certain ingredients and fragrances in soaps, shampoos, and detergents; preservatives in moisturizers and cosmetics; chemicals in hair dyes; metals such as nickel, cobalt, or gold in jewelry; and chemicals in certain plants, including poison ivy and poison oak.
Allergic dermatitis can affect people of any age, male or female, and your doctor can identify which substances you are allergic to using a patch test.
Rashes caused by allergic dermatitis appear at the location of contact and often appear within hours or days—such as when poison ivy comes into contact with the skin. If you are allergic to nickel, for instance, and wear earrings containing the metal, a rash with crusting or oozing may develop on the earlobes a few days after you started wearing them. Sometimes a rash can take as long as a week after contact to develop.
Irritant dermatitis occurs when something interferes with the normal barrier function of the skin and causes inflammation but not an allergic reaction. This happens to most people on occasion, as a result of routine exposures to irritating substances or to the environment. Common examples include chapped lips, dry hands in the winter, and diaper rash.
A person may develop irritant dermatitis as a result of repeated exposure to sports equipment such as shin guards or a helmet or frequent hand washing with harsh soaps. Acidic substances or harsh chemicals in the workplace can also cause irritant dermatitis when they come into contact with skin.
Unlike the rashes in other forms of dermatitis, the rash caused by irritant dermatitis can appear immediately at the site of exposure. Irritant dermatitis can also develop more slowly when the skin is repeatedly exposed to a trigger. The surface area, location, appearance, and itchiness of irritant dermatitis depend on the irritating substance and how much contact it has with the skin.
Nummular dermatitis appears as raised, red patches that are often very itchy. These patches are often circular, or coin-like, which is what the word “nummular” means. This type of rash can appear anywhere on the body and may last for weeks or months.
Nummular dermatitis appears most frequently in people older than age 50 but may be seen in children and adolescents too. The cause of nummular dermatitis remains unclear.