Prophylaxis

The simplest and most effective way to prevent a rash caused by allergy is to avoid the allergen. For example, many jewelry and watches are available without nickel. Also in the field of cosmetics, there are now many particularly sensitive (hypoallergenic) products.

Prognosis

A single allergic skin rash usually heals without consequences. Even if the skin appearance appears intact again afterwards, a disturbance of the skin barrier can still remain. This can promote further skin reactions and lead to a faster and stronger reaction to renewed contact with the allergen.The basic sensitization to an antigen usually lasts a lifetime.

There is no possibility of hyposensitization, as with other allergies. If the sensitization should have taken place at the workplace, a report to the respective employer’s liability insurance association should be made in any case. An allergic contact eczema is recognized in many industries as an occupational disease.

Skin rash: allergy forms

In most cases, the skin is the first organ to react to contact with a non-infectious foreign substance (technical term: allergen). A distinction must be made between different forms of this reaction. Besides urticaria and the well-known neurodermatitis, the so-called contact eczema is one of the most frequent allergic skin reactions.

Contact eczema

The so-called contact eczema (contact allergy; contact dermatitis) is a hypersensitive reaction of the skin surface to direct contact with a certain foreign substance. Shortly after contact with the allergen, reddened, swollen, weeping and/or itching areas develop on the affected skin. This rash, which occurs in the course of an allergy, can also be accompanied by the formation of blisters and/or dandruff.

Contact dermatitis, a special form of rash as a sign of allergy, is quite common and can have a variety of triggers. A classic example of an allergy that leads to the development of contact dermatitis is the so-called nickel allergy. However, other substances such as fragrances, preservatives, detergents and tanning agents can also lead to an allergic skin reaction.

With contact eczema, however, it must be remembered that it does not necessarily have to be an allergic skin reaction in every case. Non-allergic contact eczema can range from irritative phenomena (skin irritation) to toxic reactions (severely damaged skin). A contact eczema that occurs in the course of an allergy is usually located in the area of skin where the allergen contact has taken place.

In addition, this allergy-related rash can also be caused by internally absorbed non-infectious foreign substances. The hypersensitivity of the skin surface in this form of allergic rash develops over time through repeated contact with the causative allergen. Within the organism, the allergen triggers a so-called immunological sensitization.

The body’s own immune system reacts so exaggeratedly to the allergen that an allergy-related skin rash develops. In case of contact eczema, a number of possible foreign substances come into question. Among the most frequent causes of the development of such an allergy-related skin rash are Nickel (mainly in fashion jewelry, watches, spectacles, buttons, zippers, rivets) Cobalt chloride (mainly in buttons and zippers) Chromium salts (in leather) Fragrances (in cosmetics, candles and food) Phenylenediamine (in hair dyes) Preservatives Tanning agents Detergents

Nickel (especially in costume jewelry, watches, glasses, buttons, zippers, rivets)
Cobalt chloride (especially in buttons and zippers)
Chrome salts (in leather)
Fragrances (in cosmetics, candles and food)
Phenylenediamine (in hair dye products)
Preservatives
Tanning agents
Detergents

Besides contact dermatitis, the most common form of allergic skin rash is hives (urticaria).

Such a skin reaction always occurs when certain inflammatory cells in the skin are activated and release the messenger substance histamine. There are usually only a few inflammatory cells in healthy human skin. Especially the so-called mast cells play a decisive role in the development of allergy-related skin rashes.

If an allergy sufferer comes into contact with an allergen, these mast cells are activated and stimulated to release various inflammation-promoting messenger substances, especially histamine. After its release, the messenger substance histamine can pass into the surrounding tissue and dock to certain receptors on the surface of the smallest blood vessels. This gives the blood vessels the signal to expand.

In addition, the messenger substance histamine mediates an increase in the permeability of the vessel walls. In this way, more fluid can diffuse from the blood vessels into the surrounding tissue. As a result, small wheals known as hives appear on the surface of the skin of affected individuals.

Although the triggers of this form of allergy-related skin rash can be diverse, the affected persons show typical symptoms. Shortly after contact with the allergen, small to medium-sized wheals appear on the surface of the skin as a reddened rash. In addition, local swelling in the deeper tissue layers may occur (so-called angioedema).

The development of allergic urticaria is usually announced by an annoying, highly pronounced itching. In addition, in this form of allergy-related skin rash, it can often be observed that the itching increases significantly in the evening hours but decreases steadily in the course of the day. A short time after the itching appears, the typical small wheals are formed, which are irregularly bordered by a red edge.

In the presence of allergic hives, so-called angioedema can also develop in the area of the lips and eyelids. In case of an acute allergy-related rash, the itchy wheals usually disappear within 24 hours. Nevertheless, depending on the severity of the allergy, hives can flare up regularly up to six weeks after contact with the allergen.

The diagnosis of a skin rash that may be associated with an allergy is performed in several steps. Above all the detailed doctor-patient discussion (short: anamnesis) plays a decisive role in this context. During this conversation the affected patient is asked about the occurrence of the rash.

The physician asks the patient how long the current symptoms have existed and whether such skin changes have been observed at an earlier stage. In addition, the patient should consider whether there might be a connection between the occurrence of the rash and external factors. In addition, the patient is asked about other diseases and/or allergies.

Especially persons who have a so-called atopic disease, for example bronchial asthma, tend to develop one or more allergies. Internal diseases, acute or chronic infections and medications that are taken regularly (especially painkillers and anti-inflammatory drugs) also play a decisive role in the diagnosis of rashes that may be associated with an allergy. If, following the doctor-patient consultation and examination of the rash, an allergic reaction is suspected, an allergological test should be considered.

A blood test looking for specific antibodies of the so-called IgE type can also be useful. The treatment of a rash that occurs in the course of an allergy depends on the causative allergen as well as on the severity of the skin appearance and possible accompanying symptoms. An acutely occurring rash usually disappears completely within a few weeks, even without medical intervention.

During the healing phase, the formation of wheals can usually be inhibited by the administration of a so-called antihistamine.Only in very pronounced cases, which are then accompanied by other complaints, do further therapeutic steps have to be taken. Glucocorticoids, which can be applied to the affected skin areas in the form of ointments or creams, are particularly suitable for the treatment of allergic contact eczema. These drugs help to relieve the itching typical of an allergic skin reaction and have a positive influence on the healing process. Cold, moist compresses are also particularly suitable for treating acute skin rashes in the case of an allergy. In addition, the treatment of a rash that occurs in the course of an allergy consists of avoiding the causative allergen.