About Eczema
This page focuses on one specific type of eczema: atopic dermatitis. Those suffering from a different type of eczema should look elsewhere for information about their condition.
Eczema is a Skin Disease that effects millions of americans. This page should be used as a place to learn key information. If you have any questions at all please contact us if you are confused!
What is Eczema (Atopic Dermatitis)?
Eczema, and more specifically atopic dermatitis, is a chronic condition where the skin becomes dry, itchy, red, and irritated. These symptoms are associated with a weakened skin barrier. The skin barrier is the very outer layers of your skin and is responsible for helping your skin retain moisture and prevent irritating compounds from entering through your skin into the body. Atopic dermatitis episodes are often referred to as “atopic dermatitis flares” or “eczema flares”.
Atopic dermatitis can occur at any age. For some people it starts within months of birth. For others, atopic dermatitis does not arise until adulthood. It can be irritating but it's not contagious.
Eczema is hard to characterize. For some people, eczema symptoms can stop and never return; for others symptoms can occur for a lifetime. For some, skin redness is the worst symptom, for most others, itching is the worst symptom. Different people have AD arise in different body locations; so eczema can occur anywhere on the body. Today, there is no cure for atopic dermatitis.
What is the cause of atopic dermatitis?
Although scientists have not completely narrowed down the causes for atopic dermatitis, most agree that there is a genetic component to this disease. It is widely believed that people are more likely to acquire atopic dermatitis if one or both parents suffer from the disease.
It is also widely believed that the reason symptoms of atopic dermatitis arise is because the skin barrier is compromised. To understand this better, we need to examine healthy skin and then compare that to atopic dermatitis skin.
How does an eczema flare arise?
Many clinicians and atopic dermatitis advocates believe that certain environmental conditions can make an atopic dermatitis episode arise, including chemicals on the skin, soaps detergents, cosmetics, dust mites or animal dander, certain fabrics, mold or pollen. Some advocates believe that food allergies could precipitate a flare. Atopic dermatitis can arise without warning. There are a number of different “triggers” and they vary from person to person.
How do the outer layers of healthy skin stop inflammation?
The outer layers of healthy skin are an effective skin barrier that prevents allergens, irritants and bacteria from entering the body. These layers are referred to as the stratum corneum (SC). This part of the skin is important as the barrier between the body and the outside environment. Healthy SC prevents the water in our body from exiting into the environment and prevents irritants and allergens from entering the skin and causing health problems such as skin infections.
The design of the SC is similar to the design of a brick wall, and is referenced as a “brick and mortar pattern” (see figure). This design is the reason for the successful barrier created by the SC. In our skin, dead skin cells, called corneocytes, serve like the bricks in a wall and a lipid matrix (a collection of ceramides and fatty acids that “glue” the corneocytes together) serves as the mortar. The dead skin cells contain a high concentration of small molecules, which help them hold water, making it difficult for the body’s water to escape. Likewise, the lipid matrix seals the gaps between the dead cells of the SC. Since the lipid matrix is hydrophobic (repels water), this prevents water from escaping, as well as irritants and allergens from entering.
Bouwstra J, et al, Progress in Lipid Research 2003, 42: 1 - 36
One final characteristic of healthy skin is the pH. Healthy skin has a low pH, slightly less than 5.0. This pH level is known to hamper the growth of harmful bacteria, like Staphylococcus aureus, on the skin.
Note: The pH scale is a measurement system, typically ranging from 0 to 14, that determines how acidic or alkaline a substance is. A pH of 7 is neutral, values below 7 are acidic, and values above 7 are alkaline.
What is Inside Out
and Outside In?
There are two basic philosophies on the cause of atopic dermatitis that should be considered:
Inside Out
The situation where an immune system overreaction causes the skin to become inflamed. This causes atopic dermatitis symptoms like redness and itching.
Outside In
Were the skin barrier function breaks down allowing allergens, irritants, and other inflammation-inducing compounds to enter the skin causing atopic dermatitis symptoms.
What is the cause of itching in atopic dermatitis?
The itch sensation comes from two likely sources. Dry skin is just naturally itchy. However, itching usually occurs when the peripheral nerves in the skin are stimulated. The peripheral nerves create the itch sensation most often when inflammation sets in. Many of the inflammatory compounds that arise in an atopic dermatitis flare stimulate these nerves.
Itching is the most common complaint of those suffering from atopic dermatitis (as many as 77% in some studies).
The human response to itching is to scratch. This leads to what is known as the “itch scratch cycle”. When a person scratches an itchy area, it actually further stimulates these peripheral nerves to send an even larger itch sensation. More itching, more scratching until the skin is damaged enough to bleed. More damage leads to more inflammation and the cycle continues. This is why treatments to eliminate itch are so important for atopic dermatitis sufferers.
How do people’s atopic dermatitis skin differ?
Skin of atopic dermatitis sufferers is different in that the skin barrier is compromised. This allows irritants and allergens to enter, ultimately causing inflammation and the symptoms associated with atopic dermatitis.
The compromised skin barrier is caused by problems with the lipid matrix (or the mortar of the SC). The lipid matrix in atopic dermatitis has lower levels of lipids, as well as a mix of lipids that is not in the right balance. In particular, two types of lipids are not optimal: ceramides and fatty acids.
Further, when skin inflammation sets in, it causes the production of an immature and therefore less effective skin barrier. This means that more irritants, allergens and bacteria can enter and drive more atopic dermatitis symptoms.
What is the impact of S. aureus on AD skin?
S. aureus is known to cause harmful effects for atopic dermatitis sufferers. Some research suggests that S. aureus can damage the skin barrier through releasing exotoxins, which are chemicals that can damage the skin barrier. The damaged skin barrier further opens the possibility of the unwanted antigens, enzymes, and harmful bacteria that can affect deeper layers of the skin.
While the bacteria are larger and usually kept out by the skin barrier, these bacteria can enter in two ways:
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Sometimes atopic dermatitis skin dries out enough to crack the SC, which leaves large enough entry pathways for the bacteria to enter and cause inflammation.
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Channels that allow bacterial entry are created when atopic dermatitis sufferers scratch their itchy skin hard enough to form open sores.
In healthy people, the bacteria on their skin (called the microbiome) consists of a diverse number of bacteria. Most are beneficial to the skin; some can be harmful. Research shows that this healthy microbiome is supported by a pH that is acidic (~4.7).
Unfortunately, the pH of atopic dermatitis sufferer skin is higher (~ 7), which is considered a neutral pH. This higher pH level allows the growth of harmful bacteria, like S. aureus, on the skin. In addition, many of the creams used by atopic dermatitis sufferers also have a higher pH, which can actually add to the high pH problem and make it worse.
What are the symptoms of atopic dermatitis?
The most common symptoms for atopic dermatitis sufferers are:
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Dry, cracked skin
Itchiness (pruritus)
Rash or redness (color can vary depending on your skin color)
Small, raised bumps
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Oozing and crusting
Raw, sensitive skin from scratching
Thick, leathery patches of skin
Flaky, scaly or crusty skin
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Skin swelling
Why do these symptoms arise?
The important thing to remember is that if the skin barrier remains intact, the symptoms experienced by atopic dermatitis sufferers will not appear. Unless your immune system severely overreacts, eczema symptoms occur only if the skin barrier is compromised. The conundrum is that although atopic dermatitis sufferers’ skin barrier is always compromised, it does not always result in an atopic dermatitis flare. Therefore, it is difficult to know when a treatment intervention should start to avoid atopic dermatitis symptoms.
Symptoms of atopic dermatitis like skin redness, itching, and pain are inflammation-based. Once an allergen, irritant or bacteria enters the skin it stimulates the body’s response to this infection or irritation. The body sends white blood cells to combat bacteria. Inflammation inducing compounds called cytokines arrive to establish an environment to fight the infection or allergen, sometimes causing peripheral damage to the skin.
Chronic irritation can lead to other symptoms such as thickening, crusting, flaking and scaliness of the skin. Constant scratching can damage the skin leading to weeping, oozing and bleeding.