Allergies: causes, types, symptoms and treatment approaches at a glance

Chemicals, house dust and fragrances - all these substances can trigger allergies. But the body can also respond with allergic reactions to supposedly harmless or even so-called healthy things such as fruit, vegetables, trees and flowers as well as animals. In all these cases, the body reacts with defense reactions, some of which are extremely severe. And the alarming thing is that allergies are on the rise. Whereas fifty years ago allergies were considered a rare disease, today allergies are a widespread disease[1]:
In Germany, almost every fifth person suffers from an allergy. And that through all age groups from babies to seniors. In this article you will learn:

• What are allergies?
• What are typical allergy symptoms?
• How do they develop?
• Which allergies are there?
• What treatment approaches are there?

Simply put, allergies are an exaggerated reaction of the immune system. This means that the body's defense system reacts to actually harmless substances as if they were a massive danger to the body. In the case of an allergy, therefore, it is (in most cases) exclusively the overreaction of the immune system that triggers the symptoms. The physical damage in allergies is therefore a consequence of the allergic reaction. The situation is different, of course, in the case of allergies to substances that are dangerous in themselves: Chemicals [2] are also potential triggers for allergies. But depending on what they are and in what dosage the body is exposed to them, they can actually damage the body.

The immune system is programmed to distinguish between harmful and harmless foreign substances. In the case of allergy, this ability to distinguish is impaired. The reasons why the immune system reacts so exaggeratedly have not yet been comprehensively clarified [3]. However, it is known that the causes are both genetic and non-genetic. In the latter case, therefore, it is a matter of acquired allergies. It is also known that allergies occur particularly frequently in childhood and can disappear later. But in principle, allergies can occur at any other stage of life, even in old age.

The symptoms potentially caused by allergies are quite different. They affect either individual or several organs or the entire body. In addition, they can occur as an immediate type within a few minutes after contact with the allergen or with a time delay of up to two days. Symptoms can be divided into three main areas:

• Skin and mucous membranes including gastrointestinal tract.
• respiratory tract
• Cardiovascular system

The symptoms listed below can occur either alone or in combination. The list does not claim to be exhaustive:

• Skin rashes
• Rhinitis/runny nose
• Breathing difficulties up to shortness of breath
• Watery, red, burning eyes
• Asthma attack
• Cough
• Headache
• Fatigue
• Palpitations
• Diarrhea

In extreme cases, contact with an allergen can lead to a so-called anaphylactic shock. This is life-threatening and must be treated immediately by an emergency physician.

Allergy, in a nutshell, is an overreaction of the immune system. Therefore, it is first important to understand how the immune system works:

The immune system's job is to protect the body from foreign, harmful cells. Symptoms such as cough, cold and fever normally serve as defensive measures against harmful invaders. The immune system is prepared from birth or through contact with invaders to recognize harmful foreign cells.

The defense mechanism works according to a simple lock-and-key principle: an antigen, i.e. a foreign cell, has a certain surface structure. This is recognized by the immune system. The immune system produces special antibodies that fit like a key into the "keyhole" of the antigen. In this way, a specific bond is formed and the antigens can be destroyed.

In the case of an allergy, the immune system interprets substances that are mostly harmless to the body as attackers and begins the defense process. This is how the symptoms arise, which are intended to defeat a harmful invader. In the case of an allergy, however, there is no harmful intruder at all. The triggered symptoms therefore burden the affected person, although allergens in themselves cannot cause any harm to the body. This is clearly illustrated by the example of food allergies: Apples, tomatoes and celery are among the "healthy foods" in a balanced diet. Nevertheless, it is precisely these foods that trigger allergies in many people.

Allergies can have either genetic factors or non-genetic ones. In the case of genetic factors, allergies are congenital. However, allergies can also be acquired during life. Reasons for this can be:

• Allergen exposure: when affected individuals (e.g., in the workplace) are exposed to potential allergens on a large scale. This is especially true of chemicals.
• Psychological factors: High levels of stress can contribute to the body developing allergies.
• Underutilized immune system: People who are exposed to too few foreign substances during childhood (playing outside; contact with other children and animals) have an increased risk of developing allergies.

On the one hand, allergies are differentiated according to when the symptoms occur after contact with the allergen. Another distinction is to divide allergens into different groups. And finally, the allergy-causing substances are grouped together to denote allergy types.

Types of allergic reactions, according to the time of their occurrence:

• Type 1: anaphylactic type, immediate type; Here, symptoms start after seconds to minutes.
• Type 2: cytotoxic type: symptoms appear within a few hours.
• Type 3: immunocomplex type, Arthus type: symptoms appear within a few hours to max. two days.
• Type 4: Late type, delayed type: Here, between one and three days may pass before symptoms appear.

Alternatively, allergies are categorized according to the triggering symptoms. Basically, allergens cause symptoms where they enter the body.

• Skin allergies: eczema, neurodermatitis, contact dermatitis, hives.
• Allergic conjunctivitis
• Rhinitis, especially hay fever
• Gastrointestinal disorders
• Headache, especially migraine
• Anaphylactic shock

Another way to classify allergies into different groups is to group the substances that trigger the allergies, for example:

• Pollen allergies
• house dust and house mite allergies
• Allergy to animal hair and feathers
• Allergies to insect venoms
• Food allergies

It is practically impossible to cure allergies. On the other hand, it is known that allergies, as sudden as they usually occur, also disappear again in some cases. Allergies therefore do not necessarily have to accompany sufferers throughout their lives.

These are the main treatment approaches that can be used for some or more of the allergy types listed above:

• Avoidance of allergens: This is usually possible with chemicals or foods, for example. With pollen allergies, this is nearly impossible.
• Medications: These range from nasal sprays and eye drops to tablets and injections.
• Tackling the causes: Here we are talking about the so-called hyposensitization, which in principle works similarly to a vaccination.
• Prevention: The basis for a good immune system is laid in childhood. Abstaining from nicotine and alcohol during pregnancy and from nicotine in the presence of a child reduce the risk of allergies. Diet, exercise and stress reduction also play a role - throughout life.