The skin is the largest human organ and carries numerous sensory and contact functions. Special sensory cells in the skin are used to feel heat and pain and to convey tactile stimuli. The skin also has important protective functions: As a barrier, it separates the body from the environment and prevents the body from drying out and the penetration of foreign substances. Microorganisms are already recognized as germs in the skin and combated. It offers protection against UV radiation through melanin pigmentation and the hair, as well as against mechanical stress due to the special structure of the skin. The skin has the function of regulating body temperature. This thermoregulation is controlled by blood circulation (blood vessels) and sweat production.
As the body's external barrier, the skin is well protected against external environmental influences and pathogens thanks to its structure and function. Problems and illnesses such as infections, allergies or skin damage such as sunburn only occur when the skin's protective functions are dysregulated and dysfunctional. Stronger or longer exposure to UV rays or chemicals can lead to dangerous diseases such as skin tumors.
Although the skin has a successful self-protection function, it is attacked by modern lifestyles. This includes frequent cleansing with harsh surfactants (washing-active substances) and excessive or prolonged exposure to the sun. It is therefore also important to give the skin the protection it needs, such as wearing suitable (protective) clothing, using UV or sun protection, preventing injuries and avoiding harmful substances.
In the course of its development, the immune system learns to distinguish which foreign substances are pathogenic and which the body must develop a tolerance to as it is permanently exposed to these substances, such as pollen.
In an allergic reaction, the immune system reacts to a specific substance, which is referred to as an allergen, the allergy-triggering substance. As a foreign substance, this allergen is recognized by the immune system through its specific surface structure of chemical molecules, the antigens. In simple terms, allergens can therefore be chemical, plant or animal substances and the immune system uses certain characteristics to recognize whether or not they should be combated.
In the case of an allergy, there is either an overreaction of the human immune system to foreign substances that have entered the body or the immune system has not developed tolerance correctly. For example
- cleaning agents,
- cosmetics,
- hair dyes,
- preservatives,
- pollen,
- animal poisons and
- medicines
trigger allergic reactions.
In allergic reactions, a distinction is made between 4 allergy types, depending on the type of immune reaction. The most relevant allergy types in connection with the skin are the immediate type of allergy (type I) and late type (type IV) in the case of a contact allergy.
If contact with such substances causes pathological changes to occur on the skin as a result of an excessive immune reaction, patients themselves also speak of a skin allergy. However, an allergic reaction is not necessarily limited to the skin. Depending on where and how an antigen enters the body (via the skin, bloodstream, lungs, eyes, etc.), the reactions can remain localized in harmless cases (such as contact allergies) or, in extreme cases, cause reactions that affect the whole body and can be life-threatening (such as anaphylactic shock after a bee sting).
Contact allergies occur in two phases: During the sensitization phase, initial contact with the allergen takes place and certain immune cells are sensitized to the substance. On renewed contact with the same allergen, the previously sensitized cells are activated during the triggering phase, which now triggers an inflammatory reaction. This contact dermatitis leads to typical skin reactions such as redness, itching, edema or scaling. The substances that most frequently trigger contact allergies (so-called contact allergens) include, for example
- Nickel sulphate (occurrence: Closures, cutlery, medical instruments, furniture, bleaching agents, colored glazes, jewelry, clothing)
- Cobalt chloride (occurrence: as with nickel sulphate)
- Ingredients of cosmetics, cleaning agents, foodstuffs and technical liquids
- Rosin (occurrence: paper, plasters, polishes, depilatories, sports waxes)
Contact allergies occur in every age group and are very widespread in Germany.
The right person to contact if you suspect a skin allergy is a dermatologist with additional training in allergology. However, ENT specialists, pulmonologists, pediatricians and other specialists can also complete this additional training in allergology. They specialize in the diagnosis and treatment of allergological diseases. After successfully completing their training, doctors are able to carry out a wide range of allergy tests and evaluate them safely, make recommendations regarding diet and allergy prevention etc., carry out specific immunotherapy (hyposensitization) and treat anaphylactic shock in an emergency.
The diagnosis begins with a detailed medical history: in a patient interview, the allergist records the patient's medical history by asking about previous illnesses, symptoms and when they occur, medication taken and contact with certain substances. As part of the physical examination, any skin changes are examined in detail and, if necessary, a histological sample is taken, which is then examined in the laboratory. This often allows the trigger of a (contact) allergic reaction to be suspected.
There are various skin tests that can be used to further determine the allergy-triggering substance ("allergy test"). A distinction is made as to whether a contact allergy (type IV sensitization) or a type I sensitization is to be determined. Depending on the medical history, a specific test procedure is selected. Contact allergy is diagnosed using an epicutaneous test. The suspected allergens are applied to small areas of skin under standardized conditions and the skin reaction is observed. Type I sensitizations are determined using other methods, such as the rub test, prick test or intradermal tests with immediate and delayed reading (immediate-type allergy versus delayed-type allergy), atopy patch test ("patch test") and the determination of specific IgE antibodies against allergens in serum(laboratory test).
If certain preliminary tests are not informative enough, a provocation test is carried out. In a provocation test, the patient is exposed to the suspected allergen by either inhaling the substance(bronchial or inhalation provocation test), applying it to the nasal mucosa(nasal provocation test) or conjunctiva(conjunctival provocation test) or swallowing it(oral provocation test). The test is also carried out under standardized conditions and, depending on the symptoms, in emergency standby and, if necessary, in specialized clinics. The physical reaction provides information as to whether an allergy to a certain substance is present or not.
Unlike tests to detect sensitization to food allergens or moulds, skin tests to detect pollen or house dust mite sensitization are quite reliable.
Neurodermatitis, also known as atopic eczema or atopic dermatitis, is not an allergy in the sense described above, but like asthma and allergic rhinitis with conjunctivitis (including hay fever and house dust mite allergy), it is one of the three diseases of the atopic spectrum that react to contact with triggering substances with a physical reaction. The three diseases can occur one after the other or simultaneously.
Atopic dermatitis is characterized by a skin rash, eczema and severe itching. The causes are still not exactly clear, but a genetic predisposition is assumed. An enzyme defect leads to a barrier disorder in the skin, combined with a loss of water. This makes it easier for allergenic and irritating substances to penetrate the skin and damage it.
The risk of allergies can be reduced in the period between late pregnancy and the first few months of the baby's life. Even in early childhood, nutrition plays an important role. Nutrition experts recommend a varied diet and regular consumption of fatty fish, as the unsaturated fatty acids it contains have an allergy-preventing effect. The guidelines for allergy prevention, for example, make the following recommendations:
- Babies over 4 months should be exclusively breastfed
- Avoid being overweight
- Regular consumption of fish during pregnancy and breastfeeding and as a complementary food
- Avoid air pollutants and tobacco smoke
- Avoid indoor climates that are conducive to mold growth
- Vaccinations according to the recommendations of the Standing Committee on Vaccination (STIKO)
- The introduction of complementary foods should not be delayed
- No cats for children at risk; however, keeping dogs in the household is not a problem
- Prebiotics appear to have a preventive effect on atopic eczema and the consumption of vegetables and fruit, a Mediterranean diet and milk fat have a preventive effect on atopic diseases in general
The best allergy prevention is intensive education by qualified doctors. Preventive health protection also includes home furnishings. Exposure to pollutants in the air and mold should be avoided wherever possible. A varied diet with plenty of fresh fruit and vegetables already reduces the risk of allergies later on during pregnancy; avoiding certain foods has no positive effect.
