Contact dermatitis

Allergic contact dermatitis is an eczema skin disorder that is triggered by a delayed immune reaction as a specific response to an acting from outside contact allergen. This is not dangerous for the organism, the disease results only from the inadequate reaction of the immune system on the contact material. The treatment is carried out according to the principles of eczema therapy and requires uncovering the causes by patch testing. Allergic contact dermatitis is relatively common diseases, which run mostly self -limiting in unterbundenem contact with the allergen. If the causative contact allergen but not identified or not avoided, it comes to repeated episodes of illness. Careful diagnosis and Allergenmeidung are therefore of central importance.

Frequency

The lifetime prevalence of allergic contact dermatitis is estimated to be about 15%. Taking into account also other epidemiological studies, it can be assumed that the 12 - month prevalence of allergic contact dermatitis is located in Central European societies for decades stable at around 7%. Thus, the incidence of this disease is comparable to the incidence of other major common diseases such as diabetes mellitus. In contrast to such chronic diseases allergic contact eczema runs, however, self-limiting, provided the responsible contact substance is identified and avoided.

Causes and pathophysiology

Contact allergens are low molecular weight compounds, which react on the basis of their chemical reactivity to proteins of the skin. Is recognized by the immune system, a fragment of this initial complex that includes the coupled portion of the contact allergen and a peptide from the original protein.

The emergence of a contact allergy occurs in two phases: One clinically silent sensitization phase followed by a release phase, which is accompanied by skin lesions. The sensitization process is complex and is almost always unnoticed. Various conducive to now not completely understood factors or prevent sensitization.

The number of potential contact allergens is very large. Both natural products (such as phytonutrients ), as well as man-made compounds may be effective as a contact allergen. But it is the contact in the private and professional life, whether it comes to sensitization and thus potential disease. From the basic possibility to become sensitized to an allergen contact each person is affected because of the expiration of the immune response corresponds to the central processes of defense against infection, contributes to the survival of every human being. In contrast, immediate-type allergies occur (hay fever, allergic asthma, food allergies ) only in this particular group of predisposed atopic individuals. During the sensitization phase occurs in the lymph nodes to activate specific T cells that proliferate and are easily activated if renewed contact with the allergen. These cells circulate through the body and pass the preferred skin for which they have a high affinity due to specific signals.

Until a new allergen challenge ( elicitation phase ) the actual noticeable by the person concerned eczema reaction from these specific T cells is triggered by immunological messengers that lead to a non-specific inflammatory cell infiltrate immigrants. With already occurred sensitization, the contact allergic skin reaction characteristically occurs 2-3 days after the renewed contact with the allergen. This immunological reaction is called ( according to Coombs - Gell- classification), therefore also " delayed-type reaction" or type IV reaction. Because of the long persistence of the allergen-specific T- cells in the body and its dissemination in all areas of the skin, allergic contact dermatitis may also occur in any region of the body for many years after the actual sensitization in sufficient contact with the allergen.

Symptoms

The appearance of allergic contact dermatitis corresponds to a classical eczema skin reaction. The essential features of eczema are erythema (redness ), swelling, vesicles, papules ( nodules ), and scaling. Mostly all stages of eczema reaction can be run from blisters and weeping erythema to dry desquamation. For prolonged or repeated contact with the allergen, the sign of a chronic eczema with lichenification (coarsening of the skin relief), hyperkeratosis (excessive keratinization ) and fissures ( fissures ) may arise.

Diagnosis

The suspicion of development of allergic contact dermatitis often arises directly from the observed relation to the action of a contact material. If, however, during the course of a regularly recurring contact, eg at work, only after a certain time to raise awareness, so it is difficult to derive solely from the history of the cause.

The detection of contact sensitization is effected by the patch test. For this purpose, the candidate contact allergens are applied in a concentration compatible with the skin for 48 hours, with special test patches with the phenomenal free dorsal skin. If there is a contact sensitization, as a circumscribed eczema reaction at the contact point develops. Patch testing allowed the clarification of a larger number of eligible allergens and is by specialist planning, implementation and evaluation of a safe and reliable diagnostic method.

In addition to triggering by a contact allergen, the overload protective functions of the skin may lead to irritant contact dermatitis, which is very common especially on the hands. Also by the predisposition to atopic eczema ( neurodermatitis) develop through a wide variety of trigger eczema. Other causes include excessive drying of the skin reactions to bacterial colonization ( nummulär - microbial eczema) or certain yeasts ( seborrheic dermatitis). Since the clinical appearance of eczema only conditionally permits conclusions about the cause, allergic contact dermatitis can usually be proved or excluded only after a patch test.

Therapy

Unlike other forms of eczema such as irritant contact dermatitis or atopic eczema cause of the disease can easily and effectively be eliminated by avoidance of all relevant contact materials. This is the prerequisite for the success of the treatment. In general, the application of a glucocorticoid to the affected area is appropriate for heavy and especially the scattering curve forms of dermatitis, a short-term systemic treatment be necessary. The selection of the active ingredient and the pharmaceutical basis to be adapted to the diseased region, and the stage of the infection dermatitis. Therapeutic alternatives (eg, calcineurin inhibitors such as tacrolimus and pimecrolimus or UV therapy ) rarely come in allergic contact dermatitis into consideration, such as when the use of a glucocorticosteroid is contraindicated due to an already existing pre-damage the skin. Heals Eczema in the foreseeable future, despite intensive therapy from, so maybe that actually triggering contact allergen has not yet been detected and avoided or was this not consistent enough avoided because of its widespread use. If there is time and again to relapse, this can also be due to a lack of Allergenmeidung or play other causes of eczema, an additional role, as composite images of allergic contact dermatitis with eczema and irritant forms of atopic eczema are relatively common.

Forecast

A once it has arisen contact sensitization remains consist mostly live long, as it is one of the most stable forms of reaction of the immune system. A desensitization as for immediate-type allergens is not available. Therefore all the more important the consistent avoidance of incompatible materials contact through exchange of everyday products and agents, or - if this is not possible - a non-contact handling or wearing suitable gloves. As far as contact sensitization is caused by the profession, a notification to the competent accident insurance through a so-called dermatologist's report should be made. In high risk occupational groups such as the hairdressing, dentistry, metal or building trades, an insufficiently avoidable allergen exposure lead to disability.