Allergic contact eczema

from Wikipedia, the free encyclopedia
Classification according to ICD-10
L23 Allergic contact dermatitis
Allergic contact eczema
ICD-10 online (WHO version 2019)
Allergic contact eczema on the foot

The allergic contact dermatitis , the (allergy-related) contact dermatitis or allergic contact dermatitis is an eczema disease of the skin caused by a delayed immune response as a specific response to An external contact allergen is triggered. This in itself is not dangerous for the organism, the disease only arises through the inadequate reaction of the immune system to the contact substance. Treatment is based on the principles of eczema therapy and requires the detection of the causes by means of a patch test . Allergic contact eczemas are relatively common diseases that are usually self-limiting if allergen contact is prevented. However, if the causative contact allergen is not identified or not avoided, repeated episodes of illness will occur. Careful diagnostics and allergen avoidance are therefore of central importance.

frequency

The lifetime prevalence of allergic contact eczema is estimated to be around 15%. If other epidemiological studies are also taken into account , it can be assumed that the 12-month prevalence of allergic contact eczema in Central European societies has been stable at around 7% for decades. The frequency of this disease is thus comparable to the frequency of other important common diseases such as B. that of diabetes mellitus . In contrast to such chronic diseases, however, allergic contact eczema is self-limiting, provided that the responsible contact substance is identified and avoided.

Causes and Pathophysiology

Contact allergens are low-molecular compounds that react with skin proteins due to their chemical reactivity. The immune system recognizes a fragment of this initial complex, which contains the coupled component of the contact allergen and a peptide from the original protein.

A contact allergy develops in two phases: a clinically silent sensitization phase is followed by a trigger phase, which is accompanied by skin symptoms. The process of raising awareness is complex and almost always goes unnoticed. Various factors, which have not yet been fully understood, favor or prevent sensitization .

The number of potential contact allergens is very large. Both natural substances (such as phytonutrients) and artificially produced compounds can act as contact allergens. Ultimately, however, the contact in private and professional life decides whether there is also a sensitization and thus a possible illness. Every person is affected by the basic possibility of sensitizing oneself to a contact allergen, since the course of the immune reaction corresponds to central processes of defense against infection, which ensure the survival of every person. In contrast to this, immediate type allergies ( hay fever , allergic asthma , food allergies ) only occur in the group of atopics who are particularly predisposed to this . During the sensitization phase, specific T cells are activated in the lymph nodes , which multiply and can easily be activated when there is renewed contact with the allergen. These cells circulate through the organism and preferentially pass through the skin, for which they have a high affinity due to specific signals.

Only when there is renewed contact with the allergen (trigger phase) is the actual eczema reaction noticeable by the person affected triggered by these specific T cells through immunological messenger substances that lead to the migration of a non-specific inflammatory cell infiltrate. If sensitization has already occurred, the contact allergic skin reaction typically occurs 2 to 3 days after renewed contact with the allergen. This immunological reaction is therefore also called a “ late type reaction” or type IV reaction (according to the Coombs-Gell classification ). Due to the long persistence of allergen-specific T cells in the body and their distribution in all skin areas, allergic contact eczema can occur in any region of the body even many years after the actual sensitization with sufficient contact to the allergen.

Symptoms

The appearance of allergic contact dermatitis corresponds to a classic dermatitis reaction of the skin. The main characteristics of eczema are erythema (reddening), swelling, blisters, papules (nodules) and flaking . Most of the time, all stages of the eczema reaction, starting with blisters and oozing erythema, through to dry flaking are passed through. Persistent or repeated contact with the allergen can lead to signs of chronic eczema with lichenification (coarsening of the skin texture), hyperkeratosis (excessive cornification) and fissures (cracks).

diagnosis

The suspicion of developing allergic contact dermatitis often arises directly from the observed relationship to the effects of a contact substance. If, however, it occurs in the course of a regularly recurring contact, e.g. B. at work, only after a certain time to raise awareness, it is difficult to deduce the cause from the previous history alone.

The proof of contact sensitization is provided by the patch test . For this purpose, the contact allergens in question are applied to the skin-free skin of the back for 48 hours using special test plasters in a concentration that is compatible with the skin. If there is contact sensitization, a circumscribed eczema reaction develops at the contact point. The patch test allows the clarification of a large number of possible allergens and is a safe and reliable diagnostic procedure if properly planned, carried out and evaluated.

Since the clinical appearance of eczema only allows limited conclusions to be drawn about the cause, allergic contact eczema can usually only be proven or ruled out after a patch test.

therapy

In contrast to other forms of eczema such as irritative contact eczema or atopic eczema, the cause of the disease can be eliminated easily and effectively by avoiding all possible contact substances. This is the prerequisite for the success of the treatment. As a rule, the application of a glucocorticoid on the affected area is appropriate; in the case of severe and, above all, scattering forms of the eczema, short-term systemic therapy may be necessary. The selection of the active ingredient and the galenic basis are adapted to the diseased region and the stage of eczementitis. Therapeutic alternatives (e.g. calcineurin inhibitors such as tacrolimus and pimecrolimus or UV therapy ) are rarely considered in allergic contact eczema, e.g. B. when the use of a glucocorticosteroid is contraindicated because of pre-existing skin damage.

If the eczema does not heal in the foreseeable future despite intensive therapy, the actual triggering contact allergen may not yet have been recognized and avoided or, due to its widespread use, could not be avoided consistently enough. If relapses occur again and again, this can also be due to a lack of allergen avoidance or other causes of eczema play an additional role, because mixed pictures of allergic contact eczema with irritative eczema and forms of atopic eczema are relatively common.

forecast

Once contact sensitization has occurred, it usually lasts for life, as it is one of the most stable forms of reaction in the immune system. A desensitization as for immediate type allergens is not available. It is therefore all the more important to consistently avoid incompatible contact materials by exchanging everyday products and working materials, or - if this is not possible - contact-free handling or wearing suitable gloves. Insofar as contact sensitization has arisen through the occupation, a report to the responsible accident insurance company should be made in a so-called dermatologist report . In particularly endangered occupational groups such as hairdressing, dental technology, metalworking or construction professions, allergen contact that cannot be sufficiently avoided can lead to occupational disability .

Individual evidence

  1. Lothar Kerp: Allergy and allergic reactions. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition, ibid. 1961, pp. 1130-1159, here: p. 1155 ( contact allergy ).
  2. a b c guideline patch testing (PDF; 174 kB).
  3. a b guideline contact eczema (PDF; 119 kB).
  4. Guideline for dermatologist procedures (PDF; 144 kB).