How do antihistamines reduce itching


Specific allergy therapy

Allergic runny nose

When the first flowers are visible in spring, the season for sneezing fits, runny nose and sometimes itchy conjunctivitis begins for many. About 15 percent of the population suffer from a pollen allergy, also popularly known as hay fever. This allergic reaction is triggered by trees, bushes, grasses and herbs. But mold, house dust, animal hair or chemical substances such as disinfectants can also cause an allergic runny nose (allergic rhinitis). A skin prick test can often reveal what caused the allergy.

Every third pollen allergy sufferer is also hypersensitive to certain plant-based foods that are botanically closely related to the respective pollen allergen. One speaks here of "cross-reactions". For example, people who are allergic to early bloomers (birch, alder, hazel) often react to the consumption of green apple varieties, hazelnuts and stone fruit with itchy and scratchy symptoms in the palate and throat. However, cross-reactions can also lead to nausea, vomiting, asthma or even anaphylactic shock (allergic circulatory failure).

If a pollen allergy is not treated, the constant stress on the mucous membranes in the upper respiratory tract (nasopharynx) often results in a “change of floor” to inflammation of the deeper airways (bronchi). Asthmatic complaints then arise.

  • Antihistamines: Antihistamines are used to relieve hay fever symptoms. They block the action of histamine, the most important messenger substance in triggering the immediate allergic reaction. Modern antihistamines also inhibit the release of histamine from the mast cells and have an anti-inflammatory effect on the various allergy and inflammation mediators in many ways.
  • Cromoglicic acid (DNCG): Cromoglicic acid (DNCG) is suitable for the prevention of allergic rhinitis. Since it no longer blocks histamine and other mediators that have already been released, it can only be used prophylactically.
  • Corticosteroids: In severe cases of allergic rhinitis, preparations containing cortisone are prescribed, which have a strong anti-inflammatory effect. The correct dosage and type of application must be carefully observed here. The locally applied steroids are not sprayed against the nasal septum, but against the nostrils. In exceptional cases, when a quick and strong effect is required, short-term therapy in the form of tablets or injections is possible and useful.
  • Desensitization: Desensitization, i.e. gradually getting the body used to an allergen, is possible as with an insect venom allergy. An allergen extract is injected under the skin in increasing concentrations. If the treatment is continued for several years, there is at least a significant reduction in symptoms in most patients.

Allergic asthma

If an allergic runny nose is not treated consistently, the symptoms often slide one level deeper into the lungs. One then speaks of allergic asthma, also called pollen asthma. In addition to pollen, asthma patients often also react overly sensitively to the increased ozone levels on hot days. As a typical irritant gas, ozone attacks the sensitive alveoli and promotes inflammation of the airways and asthma attacks. But animal hair, dust mites or mold can also trigger asthmatic complaints.

During an asthma attack, the muscles of the bronchi cramp, the airways constrict, making it difficult to breathe out. A swelling of the mucous membranes in the bronchi worsens the shortness of breath, which can lead to life-threatening seizures. Asthmatics with allergy-related symptoms usually respond well to drugs. The course of the disease is significantly more favorable than with non-allergic asthma.

An early diagnosis of bronchial asthma is important, as treatment becomes more difficult the more severely affected the bronchial system is. Every change in therapy must be coordinated with the attending physician, because even minor changes can lead to undesirable side effects. If medication is stopped without authorization after the symptoms have improved, a relapse is often inevitable. A distinction is made primarily between those remedies that relieve the spasms in the bronchial tubes and those that inhibit or reduce the inflammation of the bronchial mucous membrane.

  • Corticoid aerosols and cromoglicic acid: Corticoid aerosols with few side effects have an anti-inflammatory effect on the bronchial mucosa and inhibit the allergy mechanisms. They increase the effect of bronchodilators, but unlike them do not help with an acute asthma attack. A good inhalation technique is important for the success of the application. An inhalation aid (spacer) ensures that the particles do not get stuck in the oral cavity. Cortisone therapy in the form of tablets or juice is only given for severe asthma. In mild asthma, the corticoid aerosols can be replaced by regular inhalation with cromoglicic acid (DNCG). Cromoglicic acid has almost no side effects and, like cortisone, is used to prevent asthma attacks.
  • Sympathomimetics and theophylline: Sympathomimetics are used to treat acute shortness of breath and for long-term therapy. They have antispasmodic properties and dilate the bronchi. Typical side effects are muscle tremors or a feeling of inner restlessness. Occurring heart problems, however, indicate an overdose with modern remedies. If the symptoms persist, especially at night, despite regular use of the metered dose inhalers, the doctor will also prescribe theophylline preparations. Theophylline occurs in numerous plants and also has a bronchodilator effect.
  • Antihistamines: In the case of allergic asthma, modern antihistamines with an additional anti-inflammatory component can alleviate the symptoms. However, they are not a substitute for asthma preparations. The anti-inflammatory properties of the newer antihistamines improve lung functions if given for at least 4 weeks.
  • Further measures: Climatic changes usually reduce the symptoms significantly. Comprehensive allergy diagnostics can be carried out in modern asthma health resorts. Breathing gymnastics is taught in order to use existing breathing reserves economically. Various methods of relaxation therapy also make it possible to control the anxiety that triggers asthma attacks.
  • Asthma training courses are offered in many cities today. Patients learn there how to deal with their illness correctly and how to adapt the medication or its dose to the current symptoms. The daily monitoring of the respiratory function with the help of a peak flow meter can determine whether the therapy is responding or whether an impending asthma attack is imminent. Regular checks of the lung functions by a doctor are always necessary so that the therapy remains optimally adapted to the course of the disease.

Food allergy

Both the natural components of every food and the preservatives, colors or flavors they contain can cause food allergies. The symptoms range from gastrointestinal complaints such as vomiting, diarrhea and flatulence to runny nose and asthma to skin rashes such as hives (urticaria). The symptoms can appear immediately after consuming the allergen or hours or days afterwards. Food allergies often play a role in the development of the aforementioned atopic diseases.

The following foods are often associated with allergies: cow's milk, chicken eggs, apples, stone and pome fruits, kiwi, tomatoes, wheat, fish, legumes, chocolate, soy, corn and nuts, almonds, raw carrots, celery, spices (anise, caraway ).

Some foods contain high concentrations of histamine (e.g. in cheese, raw sausages, strawberries, wine and beer) or substances that release histamine (e.g. in egg white, shellfish, pork and fish). Excessive consumption of such foods can lead to pseudo-allergic reactions, because histamine is one of the most important messenger substances in allergic reactions.

Since basically any food can cause an allergy, the search for the triggers is often difficult. Skin or blood tests can provide information, but are only of limited use. They can be negative because the person concerned is only allergic to the breakdown products of a food that are only produced during digestion. A positive blood test, on the other hand, does not always mean that allergic reactions have to occur. An elimination diet is therefore usually used to confirm the diagnosis. Initially, all suspicious foods are dispensed with until they are free of symptoms. Step by step, every three or more days, the eliminated foods are reintroduced and any reactions observed. Since severe reactions can occur in individual cases, this elimination diet may only be carried out in the presence of a doctor.

If an allergy to certain foods has been established beyond doubt, the best therapy is to remove these foods from the diet. If a special diet is required for this, you should seek guidance from a doctor or nutritionist.

Contact extrem

An allergic contact dermatitis manifests itself as an inflammatory reaction with reddening, swelling, blisters and itching or burning at the site of the allergen effect. The chronic course leads to crust formation, scaling and coarse skin folds. The eczema can "spread", that is, it also spreads outside the area of ​​direct allergen effects, sometimes even to other parts of the body.

Allergic contact eczema can also be triggered by substances that were previously tolerated without problems for years. Allergies to nickel salts (jewelry, watches, coins), chromate ions (cement, leather), formalin (disinfectants, textiles), fragrances, dyes, turpentine (shoe polish), but also to hairdressing substances or plant allergens are particularly common. The search for allergens is made more difficult by the fact that some substances only develop their allergenic effects when exposed to light (see also sun allergy).

  • Cortisone: The acute stage of contact dermatitis can be treated with cortisone ointments, which usually lead to rapid healing.
  • Antihistamines: Antihistamines in the form of tablets help against very severe itching. Modern antihistamines also have an anti-inflammatory effect.

Sun allergy

If the skin shows reddish, itchy eczema after exposure to the sun, the vernacular speaks of a "sun allergy". There can be very different causes behind this. In many patients, the sun is only indirectly involved in triggering the overreaction. A distinction is made between different types of diseases: e.g. the polymorphic light dermatosis, the phototoxic reaction and the photoallergic reaction.

  • Polymorphic light dermatosis: Polymorphic photodermatosis can always occur when high-energy UV rays hit skin that has not yet adapted: on vacation under the southern sun, during winter sports or in our latitudes in spring. In the course of the summer, the skin usually gets used to the UV radiation. The polymorphic light dermatosis then no longer develops.
  • Phototoxic reaction: Phototoxic reactions such as meadow grass dermatitis and bear moss dermatitis are triggered by certain ingredients of plants (e.g. fucumarins), which are also contained in some drugs (especially in many venous drugs). The picking or consumption of such plants or the use of such medications lead to severe redness with burning itching in sensitive people when exposed to sunlight. This damage occurs within the first few hours after exposure.
  • Photoallergic reaction: The photoallergic reaction usually only takes place hours after exposure to light. Two factors come together here: light and an initially non-allergenic starting material. The exposure to light creates a new molecule with allergenic properties that is now massively fought by the immune system. The triggers are mostly fatty substances, emulsifiers or chemical light filters such as oxybenzone, which - fatally - are also contained in many sunscreens. Photoallergies can also be triggered by fragrances and preservatives in cosmetics or by numerous medications such as skin preparations containing tar against eczema.
  • Antihistamines: Modern antiallergic drugs weaken the inflammatory reaction.
  • Creams containing corticosteroids are powerful anti-inflammatory. Newer glucocorticoids are skin-friendly and have few side effects when used appropriately for a short period of time.

Insect venom allergy

In Germany, up to 3.2 million people are affected by insect venom allergies, which are mainly caused by bees or wasps. The allergic reaction ranges from an intensified local reaction to burning tongue and hives to life-threatening anaphylactic shock. In anaphylactic shock, intermediary substances such as histamine are released in large quantities. They lead to vasodilatation, increased permeability of the fine blood vessels and fluid retention in the tissue. As a result, the organism is no longer adequately supplied with blood. The heart function and the circulatory system eventually break down.

In order to avoid anaphylactic shock, a doctor should be consulted if the local reaction increases. Because this can be a precursor to anaphylactic shock with the next bite. One speaks of an intensified local reaction if the radius of the reaction is larger than 5 centimeters. With the help of various allergy tests (e.g. prick or RAST tests), the doctor will quickly determine whether there is an insect venom allergy.

  • Desensitization: Desensitization is successful in over 90 percent of cases with insect venom allergies. Unless the allergic reaction goes away completely, at least all of the symptoms can be significantly reduced. Rapid hyposensitization is best, in which increasing concentrations of the diluted insecticide are injected under the skin over the course of five to six days of inpatient treatment. Subsequently, the injections must first be carried out weekly, then less frequently and in the long run every four weeks for a period of at least three years.
  • Antihistamines: Antihistamines are used to relieve stronger local reactions even during desensitization. They block the histamine receptors of the tissue cells for the histamine released by the mast cells of the skin. This will relieve itching and weaken the inflammatory response.