Allergies - from hay fever to hyposensitization

A Allergy cause the immune system to respond to essentially harmless substances we come into contact with by mounting a defensive reaction. Who is not familiar with typical hay fever, which becomes noticeable when inhaling flower pollen through symptoms such as sneezing, coughing, or swelling of the airways?

A wide variety of substances - known as allergens - such as pollen, animal hair, house dust, certain foods, or medications can allergic reactions cause. Most allergies manifest through fairly bothersome symptoms, but occasionally severe immediate reactions can also occur, triggering 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 disappear 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 one-third of women in Germany (34 percent) and more than one-quarter of men (27 percent) reported allergic reactions.

Across Europe, around 30 percent of the population is 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 grasses cause problems for only a few months each year, year-round variants such as dust mite allergies can be triggered at any time.

An  allergy test can easily detect most allergies. However, research is making only slow progress in identifying the causes of allergies. At least medications for allergic reactions are already available.

And hyposensitization can alleviate or help control some allergies. 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 . To begin with: 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 about half as many people in the former East Germany as in the former West Germany.

Just ten years later, the number of cases in East and West had nearly equalized. Allergy prevalence increased in all Western industrialized nations over the past decades, while it remained virtually unchanged in countries such as India, China, and the Balkans. One of the most important hypotheses concerning possible allergy triggers therefore focuses on individual living conditions.

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

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

A distinction is made between seasonal and year-round allergies. Flower pollen and grasses add to the air mainly from spring through autumn. Some types of pollen are even airborne well into November. However, spring and summer are the most difficult times for allergy sufferers with seasonal hay fever.

All-year 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 milder in winter because less skin is exposed to the sun and its UV index is lower during the winter months.

A cross-allergy is said to occur when symptoms of an existing pollen allergy arise after consuming certain foods. Almost two-thirds of people with pollen allergies are affected by a cross-allergy to a greater or lesser extent.

The best-known example is probably the combination of apples and birch pollen. 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 have to change their eating habits under medical supervision.

Autoimmune diseases

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

Possible triggers include viral diseases, the consequences of bacterial infections, or the overproduction of white blood cells. Some affected people have to take medication for life to suppress their immune system. In other cases, autoimmune diseases apparently heal on their own and disappear again.

The different types of allergies

The mechanism by which allergies are triggered 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. In medicine, allergies are therefore divided into four different “allergy types” .

• Type 1 allergy: Type 1 is also called the “immediate type,” because allergic reactions occur immediately or within a few minutes - after half an hour at the latest. Typical symptoms of a Type 1 allergy include skin rashes, itching, swelling, sneezing, or coughing. In severe cases, shortness of breath or anaphylaxis may occur - immediate emergency treatment can then be life-saving. In addition to pollen, dust, and animal hair, insect bites are also triggers of the immediate type.

• Type 2 allergy: Six to twelve hours after contact with the allergen, the immune system becomes active in a Type 2 allergy. It is also known as the “cytotoxic type,” because special antibodies are formed to destroy foreign structures, but in the process they 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. In this case, allergens bind to antibodies to form the eponymous immune complexes. As soon as these are absorbed by phagocytes, enzymes are released that irritate and damage the surrounding tissue. Type 3 allergy often results in inflammatory vascular diseases.

• Type 4 allergy: If allergy symptoms do not appear until at least twelve hours later, it is probably Type 4, the “delayed type.” This type, which triggers a delayed reaction, sometimes does not appear until days later and may remain active for some time even when no allergen is present anymore. Nickel allergy, for example, usually occurs as a delayed type.

What are the most common allergies?

The most common allergies are often triggered by substances that we can hardly avoid in everyday life. Mild forms are often not immediately recognized as allergies, because when enough dust or pollen gets into the nose, everyone sneezes.

Most people only realize they are allergic once the allergic reactions go beyond a normal irritation response. Other allergies can be recognized quickly based on their symptoms. Since many people nowadays are already 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: The common condition known as hay fever is caused by pollen allergies. A wide variety of plants release their pollen to fertilize one another. As tiny particles, pollen drifts through the air - when inhaled, the proteins it contains can trigger allergic reactions. Typical symptoms of a pollen allergy include sneezing, an itchy and runny nose, or watery eyes. In more severe cases, headaches or even shortness of breath leading to the development of allergic asthma may occur. It is suspected that factors such as smoking, passive smoking, or air pollution promote the development of pollen allergies. In Central Europe, hay fever is primarily caused by the following pollen: alder and hazel from January to March, ash and birch from April through summer, mugwort from August to autumn, and grass pollen from late spring through autumn. Learn more in our blog post about hay fever.

• House dust allergy: Dust accumulates in every home and is virtually unavoidable. However, dust itself causes, at most, mild irritation of the airways - house dust allergy, on the other hand, is a reaction to substances in mite droppings. These partly microscopic arachnids are practically everywhere - they live in carpets, curtains, bed linen, etc. The allergy manifests itself through cold-like symptoms, and less commonly through eye irritation. House dust allergies are rarely serious and are more bothersome than dangerous. Nevertheless, asthma can also develop in some cases. In rare cases, cross-allergies associated with eating shellfish have been reported. Normal household hygiene is generally sufficient to keep the amount of dust, and therefore the allergens, at a tolerable level. It is advisable to wipe surfaces with a damp cloth frequently so as not to stir up unnecessary dust while cleaning. Learn more in our blog post about house dust allergy.

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

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

• Contact allergies: These allergies can be very insidious because their symptoms often do not appear until twelve hours, and sometimes even days, after contact with the triggering substance. By far the most common trigger of a contact allergy is the metal nickel. Those affected may sometimes 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 develops, the contact area shows redness, swelling, or welts. In severe cases, weeping blisters may form or, in the worst case, chronic contact eczema may develop, along with thickening of the skin and scarring. Because the reaction occurs so late, severe symptoms may sometimes already occur upon the first exposure. Once the trigger is identified, it can be avoided, allowing those affected to remain symptom-free. Desensitization, as used for other allergies, is currently not possible. Learn more in our blog post about contact allergies.

• Food allergies: They are very common and exist in a wide variety of forms and manifestations. A food allergy can cause symptoms such as swollen or tingling mucous membranes in the mouth, bloating, abdominal pain, or hives. In some rare cases, however, a life-threatening anaphylactic shock may occur - peanut allergy is considered a typical trigger. While some food allergies become noticeable immediately, others are delayed-type reactions, making them extremely difficult to diagnose. Fortunately, severe food allergies are rare. Learn more in the blog post about food allergies.

• Gluten allergy: Another colloquial term often used as a general description for intolerances to wheat or the gluten protein found in various types of grain. The symptoms, which can range from bloating to severe diarrhea, may be caused by wheat intolerance or celiac disease. Severe diarrhea symptoms indicate celiac disease - an autoimmune disease affecting the lining of the small intestine. Any corresponding symptoms after consuming foods containing wheat or other grains should be medically evaluated.

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

• Drug allergies: Medicines often contain a variety of active ingredients and other substances. Some of these may trigger allergies. Allergic reactions often occur immediately after taking the medication, but they can also be delayed by hours or days. The wide range of possible triggers can make it difficult to identify a drug allergy. Relatively common and well-known allergies include allergies to ingredients in certain antibiotics or to acetylsalicylic acid (ASA), which is contained in aspirin. If a drug allergy is present, the substance in question must always be avoided. Hyposensitization is not possible. Find out more in the  blog article on drug allergies.

• Lactose intolerance: A true allergy to lactose is extremely rare. People who cannot tolerate cow's milk usually suffer from lactose intolerance. Lactose is a sugar that is also found in human breast milk. Healthy digestion breaks lactose down 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 produces typical symptoms such as flatulence, bloating, cramps, or diarrhea. Pronounced lactose intolerance requires a change in diet 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, skin rashes, or hives, an allergy could be the cause. The reason is not always immediately apparent - the finest pollen or dust particles are invisible to the human eye. Other allergies only manifest after several hours, making it difficult 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 only obtain reliable information about allergies by taking an allergy test . Consult a doctor you trust - many general practitioners or dermatologists are also allergists.

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

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

A similar method is the patch test - however, 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.

Since these allergies are delayed-type allergies, the aluminum patches often have to be worn for several days. Occasionally, blood tests or provocation tests, in which the allergen is inhaled, are also 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 extent that they cause only minor or no symptoms. In severe, life-threatening cases, the body's immune response can be suppressed with special medications.

Of course, such treatments can be associated with other side effects. If possible, it is preferable to avoid the allergy trigger completely. If this is not possible or desired - for example, because you do not want to give up your pet - hyposensitization offers the best chances 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. Through continuous contact with small amounts of the allergen, the immune system can slowly become accustomed to it. This is known as immunological tolerance.

This treatment method has already produced very good results. Allergy symptoms can be reliably reduced, and it is not uncommon for the symptoms to disappear completely after treatment. Hyposensitization can be used for immediate-type allergies - for example, pollen, dust, or animal dander allergies.

Can an allergy disappear 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 presumed recovery remain unclear. It is known, though, that allergies often become less severe over the course of a person’s life. This is probably mainly because the immune system often reacts more quickly and intensely at a younger age.

Since it is impossible to completely avoid many allergens in everyday life, a kind of “passive desensitization” probably also plays a role in allergies becoming less severe. This applies especially to “common allergies” such as pollen, dust, or animal dander 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. 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 can help you. Since some allergies can also become more severe, it is advisable to have at least an allergy test to assess the severity of any existing allergies.

Current research indicates that a healthy, active lifestyle is best suited to counteracting the development of allergies or at least severe symptoms. You often hear the famous advice to let children “play in the dirt,” because to build a healthy immune system, it needs to become familiar with potential pathogens.

Whether and exactly how an allergy develops varies from person to person. If in doubt, consult an allergy clinic to have medical professionals clarify your individual situation.

We wish you a wonderful summer - even with allergies!