October is Eczema awareness month

Posted in on October 6, 2010

Eczema (Dermatitis)

Eczema (medically known as Dermatitis) is an inflammation of the skin. Many different causes, whether allergic or irritant (like excessive dryness, physical rubbing, cold, wind, caustic chemical exposure, over washing etc...) end up looking identical on the skin.

The allergic types occur from exposure to physical contact with a substance that your immune system has a memory of fighting against (common physical contact allergens are poison ivy or oak, black hair dye, latex...). After exposure to a contact allergen the rash continues to worsen and maximize at 24-48 hours (it takes that long for the allergic cells to commute to the area of exposure). Each and every time you have a significant exposure to that contact allergen, you will have a rash. If sometimes you do have a rash and sometimes you don't, then it is not allergy based. However, intermittent exposure can keep a rash going.

One of the best ways to find out if your rash is caused by a contact allergen is to have a PATCH test. A PATCH test is done by placing small amounts of the most common allergic chemicals in tiny wells and then taping that to the skin of the back for 48 hours. When the tape is removed the wells that have a rash under them signify an allergic reaction to the contents in the well. A good history of exposure of the offending agent and a PATCH test is very helpful to finding chemicals that need to be avoided. n.b. Please do not confuse PATCH testing with PRICK testing that is common in allergists office for enhaled, food and drug allergies. We offer both types of testing. PATCH testing is done through the Dermatology department and Prick testing is done through our Allergy department.

The more common type of eczema is called Contact Dermatitis and is mainly from a breakdown in the barrier system of the skin. The integrity of the skin barrier system is affected by genetics. The epidermis (the outermost lary of your skin) is only about one millimeter thick, but has a very organized, complex anatomy. Skin cells start at the base of the epidermis (Basal cells), these Basal cells produce daughter cells continuously. These daughter cells, called Keratinocytes, are pushed to the surface of the skin and flake off as dust. As the Keratinocytes move up to the surface they have different genes turned on and off in a very precise order. These genes allow the keratinocytes to produce substances (eg, waxes and humectants -- basically substances that attract and trap water in the skin). At the top of the epidermis all these ingredients get combined to make a barrier. Think of the cells as the bricks and the barrier substance as the mortar of a wall. A well built wall or epidermis is impervious to most assaults. If one or more of the genes in the keratinocytes contains an error, then the substance that it is supposed to make is either absent or deformed and does not work to help the barrier. Genetic defects often are the most common reason for a type of inherited eczema called Atopic Dermatitis. However, even with normal genes, physical and chemical exposure can break down the barrier of skin causing eczema.

In all types of dermatitis, because of this "leaky" barrier defect, there is an out-flux of moisture from the skin and a simultaneous exposure of deep skin to substances usually kept out by the barrier. The end effect is cells deep in the skin signaling the immune system that they are "unhappy", and an inflammatory cascade occurs. In inflammation, immune cells come into the area, substances are secreted that cause the vessels to dilate and leak fluid (redness and swelling) and itching. Once the epidermis is inflamed it makes an even poorer barrier then before, and this seemingly endless cycle of inflammation and poor barrier continues.

Treatment:

If the cause is allergic, then one must avoid the offending agent. If you are not sure, then get a PATCH test to rule out most possibilities. Treatment otherwise is the same as with contact dermatitis.
If the cause is irritant it is often not easy to avoid it. Our best chance at getting over the dermatitis is to stop the inflammation long enough to have the epidermis make as good as a barrier as it can, and to  then enhance the barrier function with topical creams and ointments for maintenance.

To stop inflammation, the most powerful and common treatment is topical steroids (also called cortisone or corticosteroid). Prescription strength topical steroids work very well but need to be done with medical supervision. Other treatments that can be used are oral steroids (prednisone, Medrol, or solumedrol), anti-inflamatory type of antibiotics). There are also some weaker non steroid alternatives). Antihistamines can rarely be helpful, particularly to cause sedation and less scratching at night.

Skin hydration helps stop some of the inflammatory cascade. Increasing the humidity in the room with humidifiers can help drive moisture into the skin instead of the other way around. Even wearing damp clothing can help increase the water content of the skin. Ointments like petroleum jelly (Vaseline) and Aquafore and thick creams like Cera Ve or Eucerin Cream Original physically reduce water evaporation from the skin. Using soap substitutes like Cetaphil cleanser or Cera Ve cleanser and avoiding washclothes, loofas and scrubbing, help keep what barrier that is there intact longer. If taking a bath takes the itch away then hydrate in a bath up to twice a day. Make sure thick moisturizers are applied quickly after towel drying to trap water in the skin. Lotions are fine as long as no rash exists, but most of them have preservatives that cause stinging on rashy skin and are poor at reducing water evaporation-greasy is better.

Maintenance:

Once the rash is gone in rash prone individuals the key is to strengthen their barrier. Over the counter products that I have found helpful are Cera Ve cream and Am Lactin on a regular basis. There are also newer and more potent prescription products that we use routinely in patients with chronic problems.

Infections:

When eczema occurs for a long time on the skin it is actually oozing serum onto the surface. This may be frank oozing, but often it is more microscopic and dries and becomes crusty. Unfortunately, this serious ooze acts like a Petri dish for bacteria. The bacteria load on the inflamed skin can be heavy and cause a frank infection like impetigo (thick honey-colored crusts) or just make it difficult to heal the eczema. One very helpful method of keeping bacteria counts down is to use bleach-baths (this is also great to treat patients with MRSA). Mix 1/2 cup of bleach into a tub that is 1/2 full of water to achieve a chlorine content that is similar to the local pool water. Of course, there are times when antibiotics need to be administered.

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