Causes of pollen allergies
Pollen allergies, commonly known as hay fever (allergic rhinitis), are an excessive reaction of the immune system to normally non-harmful substances. An allergy is always preceded by an initial contact with an allergen (sensitization). The immune system reacts to the allergen and starts producing IgE-type antibodies directed against this antigen. Upon renewed contact with the allergen, the antibodies then activate the so-called mast cells, which then release substances (histamine, leukotrienes, PAF) that are responsible for the typical symptoms.
The number of allergy sufferers has been steadily increasing for many years and is expected to continue to rise in the future due to increasing industrialization and the consequences of climate change. A possible explanation for this phenomenon, is the so-called hygiene thesis. This theory originated when it was discovered that allergies occur mainly in industrialized countries and are practically absent in developing countries. The original function of IgE antibodies was to defend against parasites. However, in developed countries, diseases caused by parasitic pathogens have become rare. The theory is that by not coming into contact with the actual pathogens, a reaction against other substances (such as pollen) is favored. Due to pollutants in the air, reactions to allergens can be additionally intensified. The theory can be supported by the fact that people who live in rural areas and have a lot of contact with animals and plants also have a lower risk of allergies. Especially early in life, increased exposure to nature can have a positive effect on the immune system and potentially prevent allergies.
Allergies can also be inherited, which is also an important factor in the development of allergies.
Pollen allergy treatment options
To counteract a pollen allergy, there are generally 3 different approaches that can be used alone or in combination.
Abstinence
The first option is the so-called abstinence. This means avoiding any contact with the allergen. The feasibility of abstinence depends on the particular allergen. In the case of pollen allergy, complete abstinence is relatively difficult. It is recommended after contact with airborne pollen to change clothes and wash hair if possible. In addition, respiratory masks made of fabric or with filters can be worn. A lasting "cure" of the allergy cannot normally be achieved by allergen abstinence.
Pharmacotherapy
With the help of pharmacotherapy, allergies can only be treated symptomatically. The most commonly used drugs are the so-called H1 antihistamines. These reduce the typical symptoms of an allergic reaction by blocking histamine receptors. The most commonly used substances include, for example, levocetirizine and loratadine.
The use of glucocorticoids also belongs to the "first-line therapy". These have a positive effect on nasal symptoms and are very effective in preventing nasal congestion. This therapy is usually administered locally in the form of nasal sprays and can be used in combination with oral antihistamines. The agents used for allergic treatment are most commonly mometasone or budesonide.
Somewhat less commonly used are the mast cell stabilizers. The active ingredient cromoglicic acid is mainly used. This prevents mast cells from releasing inflammatory mediators. This can reduce the intensity of the symptoms. However, the effectiveness of this therapy is much lower than that of antihistamines and corticosteroids.
Another alternative is the short-term treatment of nasal symptoms (mainly nasal congestion or runny nose) with the help of a sympathomimetic. The best-known substances include oxymetazoline and xylometazoline. Long-term therapy with these substances is contraindicated, as they can paradoxically trigger rhinitis-like symptoms (rhinitis medikamentosa) themselves.
Hyposensitization
Allergen immunotherapy, also known as desensitization or hyposensitization, is a medical treatment for environmental allergies. In this therapy, people are exposed to increasing amounts of the allergen to change the immune system's response. Hyposensitization is currently the only way to cure allergies permanently. The therapy is considered particularly promising in patients who are allergic to one or a few substances and is more effective the earlier treatment is started.
In this therapy, allergens are repeatedly injected under the skin of the affected person or, in some cases, under the tongue at intervals of about 3 weeks. Increasing concentrations of the allergen are administered until a plateau concentration is reached. The goal of the therapy is the so-called isotype switch. The aim is to achieve a special reaction of the immune system in which antibodies are formed against the allergen, which are normally responsible for the defense against other pathogens such as bacteria and viruses (IgG type antibodies). As a result, these new antibodies recognize the allergen before it can bind to IgE antibodies, neutralizing it before an allergic reaction can develop. Crucial here are steadily increasing doses of the allergen so that the immune system "learns" that this is a harmless substance.
The effect can last for years after the treatment has ended. It is generally safe and effective for allergic rhinitis, allergic conjunctivitis, allergic asthma, and stinging insects. It is believed to be even more effective in children than in adults, but this assumption has not yet been confirmed by studies.
