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Dermatitis, Eczema

Dermatitis and eczema are interchangeable terms. Both are used to describe inflammation of the skin which may be the result of contact with a substance that causes either an irritant or allergic reaction. The inflammation is more often due to an irritant dermatitis rather than a true allergic contact dermatitis.

Irritant dermatitis
Irritant dermatitis can result from a single contact with a substance or repeated contacts. Providing that the concentration and time of exposure are sufficient, a primary irritant can induce inflammation in the skin of any person. The immune system does not play a part in irritant contact dermatitis. The damage results from chemical damage. The initial symptoms of acute irritant contact dermatitis are inflammation of the skin accompanied by burning or stinging. The initial reaction is usually directly on the site of contact. There may be several stages that the skin will progress through. Initial erythema is followed by blistering and oozing.

The secretion will dry forming scabs and finally scaling. Once the epidermis regenerates, the skin may still be red for some time at the site of contact. The reaction is most often asymmetrical and localised at the site of contact. Repeated contact with an irritant over time can lead to damage of the skin, especially in patients with a predisposition to an atopic tendency.

Allergic contact dermatitis
Allergic contact dermatitis is due to contact with a substance that produces an immune response. Substances that cause allergic contact dermatitis usually have low molecular weights and penetrate the stratum corneum. Here they need to be conjugated with a protein in order to become an antigen.

The antigen is processed by the Langerhans cells in the epidermis which results in the stimulation of T-cells. After this initial phase, there is a latent period after which the reaction phase takes place. During this phase, the T-cells fix the allergen resulting in activation of cells and an inflammatory response.

The symptoms and stages of acute allergic contact dermatitis are similar to acute irritant contact dermatitis. The initial symptoms are erythema and oedema. This is followed by the formation of vesicles, oozing and crusting then regeneration of the epidermis and scaling. The reaction is most often asymmetrical and localised. Repeated exposure to the substance which caused the dermatitis may lead to chronic dermatitis both in the case of irritant and allergic types. This can result in simultaneous occurrence of erythema, thickening of the skin and scaling, followed by lichenification.

Although these conditions have many origins, effective treatment is achieved by removing, if possible, any obvious cause and treating the skin according to its present state. Sometimes the cause of the dermatitis is hard to identify.

Strong primary irritants which cause an acute reaction are usually easy to detect. Allergens may be harder to detect. It is necessary to carefully question the patient or arrange for patch testing in order to identify these. Itching is nearly always associated with inflammation of the skin.

It is important to provide relief to break the itch-scratch cycle. However, always treat an inflamed skin with a gentle product to suit the inflammation, rather than risk an adverse reaction by using a product which is too strong. It is safer to undertreat the skin than to overtreat it. As the inflammation recedes, a gradual change may be made to a slightly stronger cream or ointment, as necessary.

Soap should not be used as it removes the natural acid protection of the skin against infection. Eczematous skin tends to have a slightly raised pH and it cannot easily return to an acid pH after washing with soap. While the skin has an alkaline pH it is more vulnerable to infection.

Advice for the Patient

1. The patient should be advised on bathing:
(a) Avoid using soap, as normal alkaline soaps will remove the skin’s natural acid protection against infection.
(b) After bathing or showering, gently pat skin dry. Do not rub.
2. To help avoid recurrences of the dermatitis, the patient needs to be advised to avoid the substance causing the reaction. This is especially important immediately after healing when the skin is sensitive.
3. The use of emollient creams will keep the skin in good condition and may help to prevent recurrences.
4. The use of gloves can help to prevent contact. A barrier cream can reduce irritation by water-based irritants.

Products to Help (Soap Alternatives, Anti-pruritics)

Pinetarsol Gel is a soap alternative which can be used to cleanse the skin when ordinary soaps are contraindicated. Pinetarsol Gel contains pine tar to relieve itching and reduce inflammation.