The term “eczema” is commonly interchanged with the term “atopic dermatitis”. This creates some confusion in terms of diagnosis. Put simply, dermatitis refers to inflammation of the epidermal or outside layer of the skin.
The dermis is a the thick sensitive layer of skin or connective tissue beneath the epidermis that contains blood, lymph vessels, sweat glands, and nerve endings.The epidermis is the thin outermost layer of the skin, itself made up of several layers, that covers and protects the underlying dermis.
Characteristics of eczema
Eczema commonly refers to a variety of skin conditions which have the following characteristics:
- Dryness (xerosis)
- Recurring skin rashes
- Redness (erythema)
- Oedema (swelling)
- Itching (pruritus)
- Thickening & markings of the skin (lichenification)
Scarring is rare with eczema, although a temporary discolouration of the skin commonly occurs. This is particularly obvious in people with darker skin and can be persistent for months or years.
Constant scratching can also cause the skin to split, leaving it prone to infection. In infected eczema the skin may crack and weep. This is often referred to as ‘wet’ eczema.
Eczema – taking a closer look
Eczema will usually present as a red and inflamed area of skin. It may be dry or it may be moist with some infection. There are usually “tell tale signs” of itching that have resulted in scattered scabs around the area or lines left on the skin from scratching.
If examined closely under a microscope you will discover that numerous changes occur to the eczematous skin:
- a change to the skin barrier
- an altered skin structure
- a loss of moisture or Trans Epidermal Water Loss (TEWL).
- the area has enlarged blood vessels in the dermis due to inflammation.
- a localized expression of pro inflammatory cytokines and chemokines. This results in the activation of other markers of inflammation including dendrites, macrophages, keratinocytes, eosinophils and mast cells.
- Between the cells there is less adhesion especially in the upper layer of the skin, subsequently contributing to scaling.
- a deficiency of a protein known as filiggrin. Filiggrin is essential for the homeostasis of the epidermal skin layer, water retention and the maintenance of a healthy skin barrier function.
- a deficiency of filiggrin also increases hypersensitivity.
- Staphylococcus aureus colonization is present. Generally the worse the colonization of staphylococcus, the worse the eczema outbreak is.
- sensitization to the malassezia spp of yeast.
- a localized changes of pH, urea and fatty acid levels.
Severe inflammation can be increased as bacteria is able to enter the damaged skin more easily. Inflammation can be compared to “a fire within”. As the severity of the inflammation increases there is increased redness and heat from the tissues. Fluid can begin to ooze from the inflamed dermis creating a crusty deposit on the surface of the skin.
With all of this happening, it is not surprising that a simple moisturizer or a cortizol cream is often not effective.
What is atopy and how is it related to eczema?
The term “atopy” refers to allergy related conditions. Included in this group are:
- hay fever
- sinusitis/ rhinitis
This condition can follow you throughout your life, but may manifest itself at different times and in different ways. For example, it
is very common for eczema to occur as an infant. This can progress to become asthma as a child. The condition may disappear completely for some years but then commonly reoccurs in adulthood as sinusitis or hay fever.
Eczema can reappear as an adult in one of the forms discussed. Remember each of these conditions are allergy related and they are linked to your genetic predisposition, your nutritional deficiencies and an immune imbalance.