As of: March 22, 2024 7:25 a.m. | from the Norddeutscher Rundfunk logo
An allergy is an overreaction of the immune system to foreign substances from the environment – such as pollen, mites or certain foods. What symptoms indicate an allergic reaction? And what helps?
Petting the neighbor’s cat, enjoying a chicken egg for breakfast or walking along a flowering meadow: What sounds like a relaxing situation to most of us can become a real problem for people with allergies. Because your body has actually declared harmless substances from the environment to be its enemy.
Allergy: what happens in the body?
The immune system tirelessly defends our body against invaders such as viruses, bacteria, parasites or pollutants from the environment. But the distinction between good and evil is not always possible. In the case of an allergy, the immune system is misdirected and switches into defense mode even when it comes into contact with actually harmless substances such as nuts, animal hair and the like – so-called allergens.
If the body’s own immune system has classified an allergen as dangerous, it usually produces antibodies specifically tailored to it. Certain immune cells, so-called T lymphocytes, are also rarely called into action. Depending on the type of immune reaction, doctors differentiate between four different types of allergies. Type I is by far the most common. Types II and III are rare.
Four types of allergies: This is how the immune system reacts to allergens
Around 90 percent of all allergies are type I – including allergies to pollen, animal hair, food and insect venom. They are also called immediate-type allergies or IgE-mediated allergies. When the immune system first comes into contact with an allergen, it produces antibodies of the IgE class (immunoglobulin E), which combine with so-called mast cells. The body becomes sensitized. He doesn’t show any symptoms yet, but is preparing himself against another encounter with the supposed enemy. If an allergen hits the antibody-mast cell connection, inflammatory messenger substances such as histamines are released. The allergic reaction follows after a few seconds to minutes – hence the name immediate type.
Type II allergy is also mediated by antibodies. They trigger a defense reaction against the body’s own cells to which allergens have docked. A typical example of this type of reaction is blood group incompatibility during a blood transfusion.
In type III allergy, immune complexes of antibodies and antigens form that can deposit in blood vessels or tissue. The result can be inflammation of the blood vessels, a so-called allergic vasculitis.
The late type is the only form of allergy that is not mediated by antibodies. Rather, contact with an allergen causes certain immune cells, so-called T lymphocytes, to become sensitized. If the T lymphocytes recognize the allergen in the blood again, they trigger an immune reaction. Complaints only occur hours or days after contact – for example in the case of contact allergies to nickel or chromium.
Symptoms: Swollen mucous membranes, skin reactions, gastrointestinal problems
An allergy can manifest itself through different symptoms and vary greatly in intensity. The eyes and nose are particularly often affected. But other areas of the body such as the skin and the gastrointestinal tract can also suffer from allergic reactions. Mucous membranes can swell, pulse and blood flow increase. Common complaints are:
Watery, itchy, burning or swollen eyes Runny or stuffy nose Frequent sneezing Cough Breathing problems Skin reactions such as rashes or itching Gastrointestinal problems such as flatulence, intestinal cramps, diarrhea, constipation Edema (swelling of the eyelids or legs, for example)
An allergy often becomes noticeable in those parts of the body that have had direct contact with the allergen. A pollen allergy often leads to problems in the nose, lungs or eyes, while food allergies affect the stomach or intestines.
Anaphylactic shock: a medical emergency
The most dangerous allergic reaction and always a medical emergency is allergic shock, also called anaphylactic shock. The risk groups primarily include people with an allergy to insect venom, a food allergy (e.g. to peanuts or seafood) or a drug allergy (e.g. to penicillin). Contact with the allergen in question can lead to a drop in blood pressure, respiratory and circulatory arrest and can therefore be life-threatening.
Allergies are on the rise
Since the 1970s, the frequency of allergic diseases has increased significantly in countries with a Western lifestyle. According to the Robert Koch Institute, more than 30 percent of adults suffer from at least one allergic disease during their lifetime. If several allergies come together at the same time, doctors speak of a tendency to allergies, a so-called allergic diathesis. But why does the immune system increasingly react excessively?
Causes: How are allergies triggered?
There are many theories about the development of allergies, but little fully confirmed knowledge. Experts assume that it is not uncommon for a combination of several triggers to lead to an allergic disease.
In addition to genetic causes – the tendency to allergies is inherited – changed living conditions and environmental influences can increase the risk of illness or intensify allergic reactions. These include increasing fine dust pollution, changing eating habits, poorly ventilated apartments, but also psychological factors such as stress.
Excessive hygiene could also play a role: these days, most pathogens are kept away by the immune system. Scientists suspect that the body’s own immune system is somewhat under-challenged and therefore attacks supposedly harmless substances from the environment.
Diagnosis: skin test, blood test, provocation test
It is not always easy to find out what the body is allergic to. Specialists in allergology can help. In an anamnesis interview, they investigate initial indications of possible allergy triggers – and then carry out appropriate tests:
Skin tests: A skin test can detect sensitization of the body to a specific allergen. The most common method used for this is the so-called prick test, in which allergen solutions are usually dripped onto the inside of the forearm and lightly pricked into the skin with a lancet. If a reaction occurs on the relevant area of skin, for example in the form of pustules or wheals, this is proof: the immune system has already formed antibodies against the corresponding allergen. If an allergy is suspected and symptoms only appear after hours or days, patch testing comes into play. The allergen solution is applied to the back using patches in order to be able to observe the body’s reaction over a longer period of time. Blood test: A blood test is often used in addition to the skin test. It can detect the IgE antibodies that are formed in most allergies (Type I allergies) in response to contact with allergens. Provocation test: The provocation test can support previous results or can be carried out if other tests have been inconclusive. Under medical supervision, the allergy sufferer’s mucous membranes are exposed to the allergen – for example through inhalation or oral ingestion. If the immune system shows an allergic reaction, the allergy is considered proven.
Treatment: Avoid allergens
The allergy triggers have been revealed – what now? Ideally, those affected avoid problematic allergens. This is especially true for severe food allergies. It is important for animal lovers to know that not every breed of dog or cat is equally allergenic. This means that the decision to have a pet can also be possible for families with a diagnosis of allergies.
When it comes to pollen or house dust mites, avoidance is difficult to implement in reality, although wearing a mask and using dust filters in the car can definitely bring some relief. People with house dust mite allergies can have special mattress covers and bed linen prescribed.
Drug treatment: hyposensitization, tablets and drops
If the symptoms are severe, hyposensitization may also be an option. The aim of such immunotherapy is to gradually get the body used to the allergy-triggering substances and thus reduce the overreaction of the immune system. Over a longer period of time, the allergen is administered initially weekly and then monthly, orally or by injection.
Many people affected by seasonal pollen allergies get some relief in the acute phase by taking tablets with active ingredients such as cetirizine, loratadine or desloratadine. These so-called antihistamines inhibit the allergic reaction. Nasal sprays and eye drops are also available in pharmacies.
Support the immune system with diet and exercise
An allergy can put an enormous strain on the body. It is all the more important not to subject an overactive, sometimes misdirected immune system to additional stress, but rather to strengthen it – for example through relaxation techniques, physical exercise or the right diet.
Choosing the right foods can also help reduce allergic reactions. The allergy leads to inflammatory processes in the body, which can be curbed by eating an anti-inflammatory diet that is healthy for the intestines.
Expert from the article
Further information
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Self-tests are intended to identify the triggers of allergies such as pollen, animal hair or nuts. This doesn’t work reliably. more
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