Allergic reaction on the skin: which allergies cause a rash?
If there's something wrong with the skin, it doesn't hide it. Redness, burning or itching are the reactions of the skin, which it signals that it does not like contact with a certain chemical or plant substance, for example. As sensitive as the skin reacts, its repertoire of means of expression is limited. “The skin speaks to us with just a few letters,” says Prof. Ulf Darsow, head of the allergy department at the Clinic for Dermatology. There could be innumerable triggers behind papules, wheals and eczema. "Even for an experienced dermatologist, it is not always easy to pinpoint the cause." Allergies are just one of many chapters - albeit one that is becoming increasingly important because there are more and more people who have allergic reactions on their own Know skin.
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What does an allergic reaction look like on the skin?
An allergic reaction on the skin can be triggered by insect poisons or food as well as a drug or just its breakdown products. A possible reaction of the skin to this, the so-called type I allergy or allergy of the immediate type, usually shows up within seconds or minutes. It can disappear just as quickly.
It is completely different with a contact allergy , which is one of the so-called late type of allergies: Only hours or even up to two days after the skin has touched a triggering substance directly does it come to blisters, sore and oozing skin areas or red, dry skin areas, sometimes with it slight swelling or fine flaking. Contact dermatitis can in principle occur anywhere on the body.
How many people have allergic reactions to the skin?
The Federal Environment Agency estimates that more than ten million people in Germany are sensitized to at least one substance. This means that the immune system has classified an originally harmless substance as "dangerous". Around six million people have already experienced acute symptoms of this sensitization in the form of a contact allergy.
What causes a contact allergy?
Substances that may contact allergy trigger, and where they occur:
Nickel : costume jewelry, jeans buttons, belt buckles, glasses frames
Fragrances : naturally or artificially produced, contained in perfumes, cosmetics, toothpaste, cleaning agents. The 26 fragrances that most frequently trigger contact allergies must be named on the products.
Ingredients of cosmetics and hair dyes : preservatives, plastics or dyes
Preservatives : only a limited number of approved preservatives, for example formaldehyde.
Natural remedies : most often Peruvian balsam, as well as arnica, tea tree oil, propolis or yarrow
Tattoo inks and henna : Contact allergies are rare, but the tattoo color pigments can spread throughout the body. In henna, the additive para-phenylenediamine (PPD) known from hair dyes can trigger allergies. This applies in particular to henna, which is used, for example, to paint the skin on the beach in holiday destinations.
Latex : for example contained in household or disposable gloves or condoms. If proteins in natural latex are the trigger, the body usually reacts within a short time with an immediate type of allergy. If, on the other hand, additives are responsible that are only added later, a late-type contact allergy often occurs, in which the skin reacts with a delay. Most of these substances initially do not pose a threat to the body.
How does a contact allergy develop?
The first episode in the history of a contact allergy is a direct encounter with the allergen - yet without an allergic reaction. "This can result in a sensitization," explains Munich allergist Prof. Ulf Darsow. “The immune system begins to classify this substance as a hazard.” If the skin comes into contact with it again, the immune system recognizes the substance as supposedly harmful - with a delay of hours or even days. In order to fight it off, it triggers inflammatory processes in the skin: the typical symptoms of contact dermatitis.
While in the immediate type of allergy antibodies that specialize in a certain allergen form, in a contact allergy certain cells of the immune system, called T cells or memory cells, take on this role. After sensitization, these memory cells recognize tiny amounts of this allergy trigger as a problematic substance when they come into contact with the skin. They release messenger substances and thus trigger a cascade of inflammatory reactions - recognizable on the skin as reddening, itching or blisters. "Because those affected experience the reaction only after a delay, it is so difficult to clearly determine the trigger," says Darsow. But this is exactly what is decisive. "Since the hypersensitivity to a substance no longer disappears and persists for a lifetime, it only helps in the long term,
How can you recognize a contact allergy on the skin?
In most cases, a contact allergy can be recognized relatively easily by the skin's appearance, reports dermatologist Ulf Darsow: The eczema swells reddish and itches, and it is not sharply defined at the edge. Unlike after a toxic reaction of the skin, i.e. when it has come into contact with a toxic substance.
How is a contact allergy diagnosed?
Allergy specialists assemble an overall picture from several individual indicators. It helps them when patients take photos of the fresh skin changes with their smartphones and bring them with them to the doctor's visit. "Every detail can be important, precisely because the contact with the cause of contact eczema was usually hours or days ago," explains Prof. Ulf Darsow. "That is detective work."
More than 3,000 substances are known to trigger allergic skin reactions. From an initially large group of suspects, as many as possible are systematically excluded. It is then crucial to use the right tests. Hundreds of substances are stored in the refrigerators of a major dermatology clinic, with which the body is exposed in minimal doses for testing purposes. In dermatological practices, there are more standardized series of the most common allergenic substances.
We have a wide range of treatments available to us, with a range of products tailored to your dermatological needs, in order to achieve the above-mentioned goals together with you.
Contact one of our specialists today for a free skin consultation to find a skincare management plan that’s right for you.