Eczema

Term of the German-speaking and European dermatological scientific area for an inflammatory intolerance reaction of the skin, which has been revised again and again with regard to its content, but ultimately has a vague definition.

In the past, eczema, from Greek "ekzema", was defined for acute, subacute or chronic, mostly pruritic, inflammatory intolerance reactions of the skin, characterized by clinically and histologically recognizable, stadial processes. The prominent clinical feature of eczema is its polymorphism, areal erythema, vesicles, erosions, papules, plaques, and scaling.

In the acute stage, eczema is characterized by exudative inflammation (vesicles, oozing, crusts); in the chronic stage, it is characterized by lichenification, desquamation, and pruritus, and in predisposed areas by rhagade formation.

Histologically, acute eczema is characterized by lymphocytic epitheliotropy, spongiosis, and possibly vesiculation, while chronic eczema is characterized by acanthosis, papillomatosis, hyper- and parakeratosis.

There are many indications that the term "eczema" will have only a historical meaning in the future (Darsow U et al. 2010) and will be completely replaced by the term "dermatitis".

The history of eczema with chronologically valid classifications

1st eczema classification

• Vulgar eczema
• Endogenous eczema
• Seborrhoeic eczema

In this classification, an adjective was assigned to the general term eczema to reveal the causal relationship. The generic term "vulgar eczema" was essentially understood to mean contact eczema, intolerance reactions of the skin caused by direct contact with exogenous substances.

Later, in leading German-language textbooks, eczema was differentiated conceptually from the term dermatitis. Dermatitis was defined as an epidermal intolerance reaction with an acute course and rapid regression, whereas eczema was defined as one with a chronic course and low spontaneous regression tendency.

2 Classification of eczema

• Atopic eczema: Atopic eczema is the most common chronic skin disease and affects people of all ages: in Germany, it is thought to be around 23% common in babies and young children and around 2-4% common in adults. Atopic eczema is accompanied by severe, agonizing itching, dry skin and weeping eczema. It often occurs on the face, neck, elbows, back of the knees and hands. Those affected usually have a predisposition to more easily irritated and sensitive skin. The exact cause is unknown, but both hereditary factors and certain triggers (e.g. wool, infections, weather conditions or stress) appear to play a role.
  
• Toxic and allergic contact dermatitis: Toxic contact dermatitis (also known as toxic contact dermatitis) occurs after contact with a substance that causes skin irritation (e.g. UV light, cleaning agents, acids or alkalis). Toxic contact dermatitis can occur in both allergy sufferers and non-allergy sufferers and appears in the area that has come into contact with the substance. In allergic contact dermatitis, skin changes are usually also limited to the area that has come into contact with the allergen (e.g. nickel or chromium). They occur approximately 24 to 72 hours after contact.
  
• Phototoxic or photoallergic eczema: The interaction between chemical substances (e.g. drugs, ingredients of cosmetics) or allergens (e.g. also drugs) with solar radiation and the skin can also cause eczema. The skin changes usually only occur in the area that was exposed to sunlight. The appearance of phototoxic eczema is similar to that of sunburn, whereas photoallergic eczema is usually more blurred.
  
• Desiccation ec zema: This form of eczema, also known as desiccation eczema or dry eczema, is caused by dehydration of the skin. The causes are a reduced oil content of the skin as well as cold temperatures, low humidity and frequent washing. Eczema often occurs on the face, arms and legs and appears as red, dry patches with a tendency to crack.dehydration eczema is particularly common in older people.
  
• Seborrhoeic ec zema: Seborrhoeic eczema usually appears in regions rich in sebaceous glands, such as the hairline of the scalp or the face, but can also affect other areas of the body. It manifests itself as yellowish, greasy scales on reddened skin. The causes of this eczema have not yet been conclusively clarified. Possible triggers are the skin-typical yeast fungus Malassezia furfur or excessive sebum production.
  
• Congestive eczema: A venous disorder (chronic venous insufficiency) is also a possible trigger for eczema. Damaged blood vessels and blood congestion (for example in the lower legs) promote inflammation, which can cause reddening of the skin, scaling, pigmentation and itching.

Compared to the older classification, vulgar eczema has been divided into acute contact dermatitis and chronic contact dermatitis according to its acuteity. Microbial eczema", which was also referred to as eczematoid microbide, was newly included. It was defined as a reactive, consecutive, immunologically induced response to a focal event. This classification makes it clear that the simple activity of an epidermal intolerance reaction hardly justifies the different terms dermatitis for "acute" and eczema for "chronic", especially as all possible transitions occur during the course of the disease. The basic error of this classification is therefore the definition of the term "dermatitis" for an acute epidermal reaction and the term eczema for the same, but now chronic, event.

The term "microbial eczema" was replaced by "discoid" or "nummular" eczema. In the meantime, the term "nummular dermatitis" has become established in international literature. In ICD10 2023, the clinical picture is also coded as "eczema nummulare, nummular eczema" under L30 "other dermatitis".

The "eczematous" disease complex, which belongs to the group of atopic diseases (Greek atopos = out of place), was summarized as "endogenous eczema". These are genetically determined, multifactorial, chronically persistent or chronically recurrent, non-contagious, usually very itchy intolerance reactions of the skin with varying degrees of acuteity, often accompanied by atopic symptoms of other organs. In the meantime, the generic term "dermatitis", i.e. atopic dermatitis, has also become established in international literature. However, the ICD 10 /2023 lists the disease complex under "atopic eczema" (see also Rożalski M et al. 2016).

Future eczema/dermatitis classification:

Contact dermatitis (contact eczema)

• Acute or chronic contact dermatitis (toxic/allergic)

Seborrhoeic dermatitis (synonym: seborrhoeic eczema)

atopic dermatitis (atopic eczema)

nummular dermatitis (microbial/nummular eczema)

Note: The 2023 version of the ICD10 states that the terms dermatitis and eczema are synonymous.

Calendula flos, borage, Avenae stramentum, Hyperici herba, Isatis radix, borage seed oil, Dulcamarae stipites, see also under Arctii radix

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2. González-Muñoz P et al (2014) Allergic contact dermatitis caused by cosmetic products. Actas Dermosifiliogr 105:822-832.
3. Knöpfel N et al. (2018) Methotrexate for severe nummular eczema in children: efficacy and tolerability in a retrospective study of 28 patients. Pediatr Dermatol 35:611-615.
4. Leung AKC et al (2020) Nummular Eczema: An Updated Review. Recent Pat Inflamm Allergy Drug Discov 14:146-155.
5. Rożalski M et al (2016). Atopic and non-atopic eczema. Acta Dermatovenerol Croat. 2016 Jun;24(2):110-5. PMID: 27477170.
6. Sohn A et al (2011) Eczema. Mt Sinai J Med 78:730-739.