Allergies - from hay fever to hyposensitization

An allergy causes the immune system to react defensively to substances that are actually harmless but that we come into contact with. Who isn't familiar with typical hay fever, which manifests when flower pollen is inhaled through symptoms such as sneezing, coughing, or swelling of the airways?

Various substances - known as allergens - such as pollen, animal hair, dust, certain foods, or medications can cause allergic reactions. Most allergies cause relatively bothersome symptoms, but severe immediate reactions can occasionally occur, triggering a life-threatening anaphylactic shock.

Contents

• What causes allergies?
• What types of allergies are there?
• The Different Types of Allergies
• What are the most common allergies?
• How can I recognize an allergy?
• Can allergies be cured?
• Can an allergy go away on its own?
• Conclusion

The likelihood of suffering from at least one allergy is high. A 2022 survey by Statista Research showed that just over a third of all women (34 percent) and more than a quarter of men (27 percent) in Germany reported allergic reactions.

Around 30 percent of the population across Europe are considered “allergic,” although the number, type, and severity of allergies vary greatly from person to person. While seasonal allergies, such as allergies to pollen and grass, cause problems for only a few months a year, year-round varieties such as dust mite allergies can be triggered at any time.

An allergy test can easily detect most allergies. Research, however, is only slowly uncovering the causes of allergies. At least medications for allergic reactions are already available.

And hyposensitization can reduce the effects of some allergies or make them manageable. This article presents current knowledge about allergies, and you will learn interesting facts about various allergies, possible causes, consequences, and treatment options.

What causes allergies?

Allergies can have various causes . One thing up front: it seems that the number of allergy sufferers is steadily increasing, especially in the Western world. Medical data from the first years after reunification show that hay fever affected only half as many people in the new federal states as in the old federal states.

Just ten years later, the number of cases in East and West had nearly evened out. Over the past decades, the prevalence of allergies has risen in all Western industrialized nations, while it has remained practically unchanged in places such as India, China, or the Balkans. One of the most important hypotheses about the possible causes of allergies therefore focuses on individual living conditions.

The so-called hygiene hypothesis holds that an under-challenged immune system - especially at a young age - can lead to the development of allergies. Put simply, children in Western countries do not “play in the dirt” enough. As a result, they lack sufficient contact with different bacteria, which “train” the immune system’s T helper cells.

As a result, T helper cells would later mistake harmless substances for dangerous ones and trigger corresponding immune responses. According to this hypothesis, growing up close to nature, with plenty of contact with animals and plants, and overcoming various illnesses as a child should reduce the likelihood of developing allergies.

A distinction is made between seasonal and year-round allergies. Pollen and grasses are especially abundant in the air from spring to fall. Some types of pollen are even airborne well into November. However, spring and summer are the most difficult seasons for people with seasonal hay fever.

Year-round allergies are those that are “always there,” because allergens such as house dust, nickel, latex, or peanuts can trigger an allergy at any time of year. A sun allergy is often less severe in winter because less skin is exposed to the sun and its UV index is lower during the winter months.

A cross-allergy occurs when symptoms of an existing pollen allergy appear after eating certain foods. Almost two-thirds of people with pollen allergies are affected by cross-allergies to a greater or lesser extent.

Perhaps the best-known example is the combination of apple and birch. The birch pollen allergen is so similar to the allergen found in apples that the immune system treats the substances in the same way. If a cross-allergy is severe, those affected may need to change their eating habits under medical supervision.

Autoimmune diseases

Autoimmune diseases are particularly tricky because they cause the immune system to attack the body's own cells and tissues. A well-known example is “lupus,” which causes chronic inflammation of connective tissue, joints, and various organs. Diagnosing and treating autoimmune diseases poses major challenges for doctors.

Possible causes include viral diseases, the effects of bacterial infections, or an overproduction of white blood cells. Some people affected have to take medication for the rest of their lives to suppress their immune system. In other cases, autoimmune diseases seem to heal on their own and go away.

The Different Types of Allergies

The mechanism that triggers allergies in the body does not always work in the same way. There are also differences in how allergens enter the body and how long it takes for the first symptoms to appear. Allergies are therefore divided into four different “allergy types” in medicine.

• Type 1 allergy: Type 1 is also called the “immediate type” because allergic reactions occur immediately or within a few minutes - no later than half an hour. Typical symptoms of a type 1 allergy include rash, itching, swelling, sneezing, or coughing. In severe cases, shortness of breath or anaphylaxis can occur - immediate emergency care can then be lifesaving. In addition to pollen, dust, and animal hair, insect bites can also trigger the immediate type.

• Type 2 allergy: In a type 2 allergy, the immune system becomes active six to twelve hours after contact with the allergen. It is also known as the “cytotoxic type” because special antibodies form to destroy foreign structures, but in the process attack the body’s own tissue. This type of allergy often occurs in connection with blood transfusions.

• Type 3 allergy: The so-called “immune complex type” also becomes noticeable after six to twelve hours. Allergens bind with antibodies to form the eponymous immune complexes. Once these are absorbed by phagocytes, enzymes are released that irritate and damage the surrounding tissue. Type 3 allergies often result in inflammatory vascular diseases.

• Type 4 allergy: If allergy symptoms do not appear until at least twelve hours later, it is likely to be a type 4, or “delayed-type,” allergy. This type, which triggers a delayed reaction, sometimes does not appear until days later and can remain active for a while even when the allergen is no longer present. Nickel allergy, for example, usually appears as a delayed-type allergy.

What are the most common allergies?

The most common allergies are often triggered by substances that are difficult to avoid in everyday life. Mild cases are often not immediately recognized as allergies, because everyone sneezes if enough dust or pollen gets into their nose.

Most people only realize they have allergies when their allergic reactions go beyond the normal response to irritation. Other allergies are easy to recognize from their symptoms. Since many people today are aware that allergies exist, initial allergy tests are often carried out as early as childhood.

Here is an overview of some of the most common allergies:

• Hay fever: Behind the common ailment known as hay fever are pollen allergies. A wide variety of plants release their pollen to fertilize one another. Pollen drifts through the air as tiny particles - when inhaled, the proteins it contains can trigger allergic reactions. Typical symptoms of a pollen allergy include sneezing, an itchy, runny nose, or watery eyes. In more severe cases, headaches or even shortness of breath can occur, potentially leading to allergic asthma. Factors such as smoking, passive smoking, or air pollution are thought to promote the development of pollen allergies. In Central Europe, hay fever is mainly caused by pollen from the following plants: alder and hazel from January to March, ash and birch from April into summer, mugwort from August into autumn, and grass pollen from late spring through autumn. Find out more in the blog post about hay fever.

• Dust mite allergy: Dust accumulates in every home and is virtually unavoidable. But dust itself causes at most mild respiratory irritation - dust mite allergy, on the other hand, is a reaction to substances in mite droppings. These tiny, sometimes microscopic arachnids are practically everywhere - they live in carpets, curtains, bed linens, etc. The allergy causes symptoms similar to a common cold, and less often eye irritation. Dust mite allergies are rarely severe and are more of a nuisance than a danger. Nevertheless, asthma can develop in some cases. Cross-allergies triggered by eating shellfish have also been reported in rare cases. Normal household hygiene is usually enough to keep dust levels, and therefore allergen levels, tolerable. It is recommended to mop with a damp cloth frequently to avoid stirring up unnecessary dust while cleaning. Find out more in our blog post about dust mite allergy.

• Pet hair allergy: Here, too, the name of the allergy is somewhat misleading, because the hair of popular pets such as dogs and cats is not what causes the problem. In fact, the allergies are caused by certain proteins in animals’ saliva. During grooming, these proteins get onto the animals’ fur and, along with shed hair, throughout the home. The allergens can remain airborne there for a long time because they consist of tiny particles. “Pet hair allergies” are most commonly triggered by cats, closely followed by dogs. People with cat allergies are usually allergic to all types of cats, although some produce lower amounts of allergens in their saliva. People with dog allergies are sometimes allergic to only certain breeds. The symptoms often resemble a cold, and swollen, watery eyes are also typical. Frequent cleaning of rooms used by pets, as well as installing air purifiers, can help reduce allergen exposure. Read more in our post about pet hair allergy.

• Sun allergy: If hives, blisters, or an itchy rash appear one or two days after sun exposure, you are probably hypersensitive to UV radiation. Technically, “polymorphic light eruption” is not an allergy. The exact causes are still unknown, but this overreaction often occurs when the skin is exposed to more sunlight again after the winter months, and then subsides. Anyone prone to severe symptoms should seek medical advice - sometimes the skin can gradually be accustomed to UV light again through light therapy. Learn more in the blog post about sun allergy.

• Contact allergies: These allergies can be very tricky, as their symptoms often appear only after twelve hours, sometimes even days after contact with the triggering substance. By far the most common cause of a contact allergy is the metal nickel. Those affected may be unable to wear nickel-containing jewelry or may need to ensure that their skin does not come into contact with metal buttons. When the allergy flares up, the contact area develops redness, swelling, or welts. In severe cases, weeping blisters may form or, in the worst cases, chronic contact eczema may develop, along with thickening of the skin and scarring. Because the reaction occurs so late, severe symptoms can sometimes occur the very first time. Once the trigger is identified, it can be avoided and those affected remain symptom-free. Desensitization, as with other allergies, is not yet possible. Learn more in our blog post about contact allergies.

• Food allergies: They are very common and exist in many different forms and variations. A food allergy can cause symptoms such as swelling or tingling in the mucous membranes of the mouth, bloating, abdominal pain, or hives. In some rare cases, however, it can also cause a life-threatening anaphylactic shock - peanut allergy is a typical trigger. While some food allergies cause immediate symptoms, others are late-onset, making them much harder to diagnose. Fortunately, severe food allergies are rare. Learn more in the blog post about food allergies.

• Gluten allergy: Another colloquial term that is often used broadly to refer to intolerances to wheat or to the gluten protein found in various grains. Symptoms, which can range from bloating to severe diarrhea, may be caused by a wheat intolerance or celiac disease. Severe diarrhea is a sign of celiac disease, an autoimmune disease affecting the lining of the small intestine. Any symptoms that occur after eating foods containing wheat or other grains should be evaluated by a doctor.

• Insect sting allergy: An allergy to insect venom can cause wasp or bee stings to trigger severe, sometimes even life-threatening, immediate reactions. Stings in the throat and mouth area, or even inside the mouth or throat, are particularly dangerous. The resulting swelling is dangerous even for people without allergies - with an insect venom allergy, the swelling is so severe that it poses an acute danger to life. Cramps, diarrhea, vomiting and a racing heart can be further symptoms of an insect sting allergy. Find out more in the blog post on insect sting allergies.

• Medication allergies: Medications often contain a variety of active ingredients and other substances. Some of these can sometimes trigger allergies. Allergic reactions often occur immediately after taking the medication, but can also be delayed by hours or days. The many possible triggers can make it difficult to identify a medication allergy. Relatively common and well-known allergies include, for example, allergies to ingredients in certain antibiotics or acetylsalicylic acid (ASA), which is found in aspirin. If you have a medication allergy, you must always avoid the substance in question. Desensitization is not possible. Find out more in the blog post on medication allergies.

• Lactose intolerance: A true allergy to lactose is extremely rare. People who cannot tolerate cow's milk usually have lactose intolerance. Lactose is a sugar that is also found in human breast milk. A healthy digestive system breaks down lactose into glucose and galactose in the small intestine - with an intolerance, lactose is not digested properly and is only broken down in the large intestine. This causes typical symptoms such as bloating, a feeling of fullness, cramps or diarrhea. Severe lactose intolerance requires dietary changes under medical supervision. However, it is not life-threatening.

How can I recognize an allergy?

If you frequently experience symptoms such as watery eyes, itching, sneezing, rashes or hives, an allergy could be the cause. The reason is not always immediately obvious - even the tiniest pollen grains or dust particles are invisible to the human eye. Other allergies only cause symptoms hours later, making it harder to identify the cause.

Try to remember whether the symptoms occurred in connection with a food, taking a medication, or an insect bite, and how long it took for the symptoms to appear. If you seek medical advice, you will be asked about this, among other things.

You can get reliable information about allergies only by taking an allergy test . See a doctor you trust—many general practitioners and dermatologists are also allergists.

In most cases, a skin test is performed for this. The standard method is the so-called prick test. Allergens dissolved in a neutral liquid are dripped onto the skin. A fine needle is used to pierce the upper layer of skin through the drops, allowing a small amount of the allergen to seep into the skin.

If the affected area swells over the next few minutes, an allergy is present. This method can be used to test for numerous allergies and their severity at the same time—usually on the skin of the back.

A similar method is the patch test —however, small aluminum discs are placed on the skin after being coated with a mixture of allergens and petroleum jelly. This method is used to identify contact allergies.

Because these are delayed-type allergies, the aluminum patches often have to be worn for several days. Blood tests or challenge tests, in which the allergen is inhaled, are also occasionally used to diagnose allergies.

Can allergies be cured?

According to current scientific knowledge, allergies cannot be cured. However, they can usually be treated and, in some cases, suppressed to the point that they cause only minor symptoms or none at all. In severe, life-threatening cases, the body’s immune response can be suppressed with special medications.

Of course, such treatments can come with other side effects. If possible, it is preferable to avoid the allergen completely. If this is not possible or desired—for example, because you don’t want to give up your pet—hyposensitization offers the best chance of success.

During hyposensitization , patients are deliberately given small amounts of the allergen. Treatment begins with an extremely low dose, which is gradually increased over weeks and months. Continuous exposure to small amounts of the allergen can slowly help the immune system get used to it. This is known as immunological tolerance.

Very good results have already been achieved with this treatment method. Allergy symptoms can be reliably reduced, and not infrequently, the symptoms have even disappeared completely after treatment. Hyposensitization can be used for immediate-type allergies - for example, pollen, dust, or pet hair allergies.

Can an allergy go away on its own?

There are reports of cases in which allergies are said to have disappeared again for no apparent reason. However, these cases are rare, and the reasons for the supposed recovery are unclear. It is known, however, that allergies often become less severe over the course of a person’s life. This is likely mainly because the immune system often reacts more quickly and intensely at a younger age.

Since it is impossible to avoid many allergens completely in everyday life, a kind of “passive desensitization” probably also plays a role in allergies becoming less severe. This applies in particular to “common allergies” such as pollen, dust, or pet hair allergies.

Conclusion

Allergies are part of our lives, and in most cases it is possible to live with them. Hyposensitization in particular has already helped many people affected by allergies. If you suffer from a severe allergy, you should never rely on it becoming less severe or healing spontaneously.

Consult a doctor, as in many cases they will be able to help. Since some allergies can become more severe, it is advisable to have an allergy test at least to assess the severity of any existing allergies.

Research suggests that a healthy, active lifestyle is best suited to preventing allergies from developing, or at least keeping them from becoming severe. You often hear the famous advice to “let children play in the dirt,” because a healthy immune system needs to encounter potential pathogens as it develops.

However, whether and exactly how an allergy develops varies from person to person. If in doubt, visit an allergy clinic to have medical professionals assess your individual situation.

We wish you a wonderful summer - even with allergies!