Atopic Dermatitis (Eczema)
Why do atopic people get eczema?
How is atopic eczema diagnosed?
What is dermatitis?
"Dermatitis" literally means "inflamed skin." The term, dermatitis, is used to describe the skin when it is irritated, red, or inflamed. For example, sunburn, hives, or the rash of measles may be described as dermatitis.
What is eczema?
Eczema is a specific type of dermatitis. With eczema, the skin is not only inflamed (dermatitis), but it also is oozing. Early on, the oozing may show up as small blisters ("vesicles"). After a few days, the blisters usually break open and dry up, leaving scabs or crusts. After several weeks, the oozing is only visible under a microscope. At this stage, eczema looks dry and scaly.
What causes eczema?
Eczema is a reaction pattern of the skin. There are numerous causes, or triggers, of eczema. Some cases are triggered by contact allergy, such as poison ivy. More often, eczema is a reaction to external irritation. For example, rubbing the skin (scratching) may cause an eczema reaction. Harsh chemicals, detergents, and excessive washing also can cause it. Generally, eczema does not result from internal causes, such as foods or medications. More often, internal triggers cause a different type of inflammation (dermatitis), called hives or urticaria.
What is atopy?
Atopy, meaning "without a place," is a word invented in 1923 by Drs. Cooke and Coca, who were classifying and categorizing different skin conditions and rashes. They had a group of patients who had unusually sensitive skin, and who were very susceptible to irritation and eczema. Most of these patients also had family members with hay fever, allergies, or asthma. Since this group of patients did not fit in Dr. Coca's classification system, he made up the word, atopy, to describe them. Today, atopy is considered an allergic condition that a person may inherit.
What causes atopy?
It is not known why atopic people have sensitive skin. Most atopic people begin having eczema by two years old. If one parent is atopic (i.e., has hay fever, asthma, or allergies), there is a 20% chance that the child also will be atopic; when both parents are atopic, there is a 60% chance. However, to develop eczema, there must be a cause, such as irritation. Therefore, the skin sensitivity and easy irritation is inherited, while eczema is not.
Human skin is designed to act as a barrier to keep water inside the body and to keep irritants outside the body. In atopic people, the barrier does not work correctly, and the water evaporates easily, leading to very dry skin. Atopic people also perceive the sensation of itch more easily. When clothing slides across the skin, most people feel a sensation of touch or tickle, but atopic people feel a sensation of itch. Skin sensitivity and skin barrier function generally improve with time. Fifty percent of people stop having skin irritation and eczema by age 5, and 90% of people stop by age 9. Sometimes, eczema reappears in adults, usually after age 60.
Why do atopic people get eczema?
Atopic people itch more easily, more intensely, and more frequently than other people. Scratching-which triggers a rash-is believed to be the cause of eczema in atopic people. In fact, eczema in atopic people has been called "the itch that rashes." Two experiments support this theory. If you gently scratch anybody's skin for 15 minutes every day, you will produce the eczema reaction. Once the eczema reaction appears, the skin usually itches so much that people will keep scratching. Unless you interrupt the itch/scratch cycle, eczema cannot heal. On the other hand, if you put a protective cast over the eczema, it will heal very quickly, even without any other treatment.
Eczema can be triggered by any kind of irritation, not just scratching. Since the skin barrier in atopic people does not work correctly, rough wool clothing, strong soap, frequent bathing, or stress can easily trigger eczema. Because atopic skin loses water easily, eczema is often worse in dry winter months. Generally, atopic eczema is not caused by contact allergy or by food allergy.
What are the common findings?
Atopic people often have a small crease on the lower eyelid near the nose ("Dennie's Pleats"). They may have dark circles under the eyes, probably from the closely associated hay fever/allergies. They may have small acne-like bumps on the backs of the arms. The wart virus and the ringworm/athlete's foot fungus grow more easily on atopic skin. These findings help to identify atopic people even if they never have skin irritation or eczema.
Eczema always looks the same, no matter what causes it. It is red, scaly, crusted, or blistered. In infants, eczema is usually located on the scalp ("cradle cap"), cheeks, elbows, and knees. These areas are most affected in infants, because they cannot directly scratch with their fingers, but they can rub against bedding or other surfaces. In toddlers, eczema mostly occurs on the areas where skin can touch itself, like the creases in front of the elbows or behind the knees. In adults, eczema is rare (they usually have only hay fever or asthma), but it may occur on the hands and feet.
How is atopic eczema diagnosed?
For atopic eczema to be diagnosed, itch and eczema must occur. Eczema also must last for a long period of time, or it must appear frequently. Eczema should be in the classic location for the age of the patient. When a person is diagnosed with atopic eczema, another family member usually is atopic.
How is atopic eczema treated?
The goal in treating eczema is for a child to be comfortable and still be able to function; it is not as important to make every last spot of eczema disappear. To treat the inflamed, itchy rash areas, most pediatricians and dermatologists will use very mild prescription strength cortisone (steroid) creams. These creams are applied two to three times daily until the rash clears, or the itching stops. The cortisone will penetrate the skin better if a damp cloth is applied after the medicine. Damp pajamas or long john underwear also may be used. Oral antihistamines, such as Benadryl, reduce the sensation of itch and increase drowsiness to ensure restful sleep. Topical antihistamines do not work. Occasionally, us will prescribe antibiotics when the raw, irritated skin gets infected. Dietary manipulation generally does not work. Severe cases may require a special kind of ultraviolet light treatment or powerful anti-inflammatory medicines.
What are the complications?
Eczematous skin gets infected more easily, especially by the cold sore virus. People with active eczema should not touch a cold sore. In darker skin, eczema and other skin irritation may leave dark spots. Dark spots always resolve without treatment, but it may take several months. The intensity of itching may prevent restful sleep; therefore, young patients may be tired or grouchy during the day.
How is eczema prevented?
Eczema cannot be completely prevented, but it can be less severe and less frequent. Dry skin always itches easier and more severely than moist skin. Humidifiers are helpful. Thick cream moisturizers, applied very frequently, and especially after bathing, also are beneficial. Young children should bathe less frequently with less soap. All soap is very irritating, especially Ivory and deodorant soaps. Soap substitutes, like Cetaphil, are excellent. Soap substitutes can be massaged gently onto the skin and simply wiped off. They do not need to be rinsed. In addition, cotton clothing is less scratchy than most synthetics or wool clothing. To remove irritating soap residue, clothing should be double rinsed in the laundry.
What research is being done?
Currently, most of the research on eczema is focused on developing better and safer anti-inflammatory medications, both topical and oral. Significant research also is underway to better understand and correct the barrier abnormality of the skin. To review recent research articles, go to http://www.nlm.nih.gov and search "pubmed" on your Internet browser.
Links to other information
A list server is available for patients with eczema. Send an e-mail to email@example.com and type "subscribe eczema" in the subject line.
For eczema support group information, call or write to:
National Eczema Society
163 Eversholt Street
London NW1 1BU, United Kingdom
Phone: 0171 388 4097
Fax: 0171 388 5882
American Academy of Dermatology https://www.aad.org/dermatology-a-to-z/for-kids/about-skin/eczema-itchy-skin/what-is-eczema
About the Author
After finishing medical school and dermatology training at the University of Oklahoma, Paul came to Colorado to further his knowledge in this specialty.
He is board certified in Dermatology and Dermatopathology. He works at a busy private practice with offices in Aurora and Parker, Colorado. He also teaches at the University of Colorado Department of Dermatology.
Copyright 2012 Paul Gillum, M.D., All Rights Reserved
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