What causes seasonal allergies?

What causes seasonal allergies?

In the case of an allergy, the immune system reacts hypersensitively to harmless foreign substances (allergens) such as plant pollen or certain foods. As a result, the symptoms are sometimes only mild but can be very stressful and restrict everyday life.

There are various ways to treat an allergy. Some allergy triggers can be avoided – others can hardly be avoided. What causes seasonal allergies are:

• Pollen
• House dust mites
• Domestic and farm animals
• Insect venom
• Food
• Medications
• Contact allergens (for example, metals or fragrances)
• Molds

Allergic reactions occur most frequently in the respiratory tract, the skin, and the mucous membranes. The symptoms usually occur immediately after contact, sometimes only after hours or days.

Allergies are also called hypersensitivities. However, some hypersensitivities have nothing to do with an allergy. These include specific intolerances to foods (intolerances). Since the symptoms can be similar, a thorough medical examination is essential. If it is determined that an allergic reaction causes the symptoms, they can be treated accordingly.

Symptoms

Typical symptoms of allergies are:

• Rhinitis, coughing, and sneezing
• breathing problems
• watery eyes
• itching
• skin rash
• swelling of the mucous membranes
• gastrointestinal problems

Most often, the body parts that have direct contact with the allergy trigger (allergen) react. For example, foods can cause itching and swelling of the mouth and tongue. In addition, the upper respiratory tract comes into contact first with pollen, resulting in a runny nose or sneezing.

Seasonal hay fever is only noticeable during the pollen flight. However, allergies to dust mites or pets can cause symptoms all year round, as the allergens are not only in the air we breathe in spring or summer. In the case of allergies to medicines and insect venom, the complaints are limited to individual situations but are often much more severe.

In the case of an allergy to food, insect venom, or certain active ingredients of medicines, an anaphylactic reaction may occur. It is an emergency and can be life-threatening. In this case, the symptoms also spread to other body areas, such as the gastrointestinal tract, respiratory tract, or cardiovascular system. An anaphylactic reaction can cause itching, swelling, abdominal pain, nausea, vomiting, impaired consciousness, shortness of breath, and a drop in blood pressure, among other symptoms.

Causes and risk factors

The tendency to an allergy often runs in families. Experts call such a tendency “atopy.” Whether an allergy develops from it depends, among other things, on environmental influences. For example, air pollution and cigarette smoke can promote allergies and secondary diseases such as asthma.

In an allergic reaction, the body’s immune system reacts to specific foreign proteins (allergens) that are harmless, as if to a pathogen or foreign body. For example, House dust mites or food typically pose no danger to the body – but in the case of an allergy, they trigger symptoms. The immune system forms defensive substances (IgE antibodies) against these substances because it considers them harmful and tries to fight them.

These antibodies form on first contact with the allergen and bind to specific cells. This process is called “sensitization.” If contact occurs again afterward, these cells release chemical substances, including histamine tissue hormone. These substances then trigger allergic reactions such as sneezing, coughing, or a skin rash.

Frequency

About every third person in America is diagnosed with allergic diseases in their life. In addition, about 20 to 25 % of all children and adolescents have hay fever, asthma, or neurodermatitis. In the last 30 years, the number of people with allergies has increased.

Course

Allergies usually begin in childhood and adolescence and often persist throughout life—however, some regress in adults. For example, specific food allergies, such as milk or hen’s eggs, can also disappear again – a peanut allergy usually does not. Whether an allergy can disappear depends on the trigger.

The symptoms are often only mild at first and become more severe over time. Sometimes other diseases are added. For example, hay fever can lead to a floor change over many years. Then, the symptoms move to the lower respiratory tract, and asthma develops. Allergies can also promote neurodermatitis.

An allergic reaction to pollen, for example, can be accompanied by an allergy to certain foods. Then one speaks of a cross allergy. A cross-allergy occurs because the different allergens contain similar proteins to which the immune system reacts.

Diagnosis

During the medical consultation, the patient is first asked about their symptoms, life circumstances, and medical history. Then, there are various tests to detect an allergy:

Prick test:

this test is used when an allergy such as hay fever is suspected, in which a reaction is seen immediately after contact with the trigger. For the test, possible allergens are applied to the forearm at some distance from each other. The skin is then lightly scratched at these points to allow the allergens to enter the skin. If the skin in these areas becomes red and swells similar to a large mosquito bite, it is an allergic reaction.

Epicutaneous test (patch test):

This test is suitable for suspected allergies that only become noticeable half a day to 3 days after contact with the trigger. For this, a patch with the suspected allergen is stuck on the back for 1 to 2 days and checked whether the skin swells, reddens, and itches.

Provocation test:

In this test, you are exposed to various allergens and checked to see if you react to them. If allergic rhinitis is suspected, allergen extracts are applied to the nasal mucosa with a spray or drop form. If the mucous membrane swells, you sneeze, and your nose starts to run, this indicates allergic rhinitis. A provocation test is usually only done if the other tests have not given a conclusive result.
Sometimes a blood test (laboratory test) may also be necessary to find antibodies against specific allergens: for example, if a skin test is too risky or the result was inconclusive. In addition, not all allergens are suitable for a skin test.

Specialists offer allergy tests focusing on allergology, usually dermatologists, ENT specialists, pulmonologists, or pediatricians.

Prevention

Developing an allergy often cannot be prevented. However, specific measures may be able to reduce the risk somewhat. For example, children who were exclusively breastfed for the first 4 to 6 months of their lives are slightly less likely to develop allergic asthma. However, according to studies, this makes little difference for other ailments such as allergic rhinitis. Non-smokers and children who grow up in a smoke-free environment also lower allergy risk.

If there is a high risk of allergy, it may make sense not to keep a cat to encourage cat allergy. However, if there is no increased risk of allergy, giving up pets is unnecessary.

Treatment

The following options are available to relieve allergy symptoms:

Avoid contact with allergens:

How well this works depends primarily on the trigger type. Certain foods or chemical substances can usually be avoided quite well. In contrast, it is almost impossible to protect oneself from pollen. However, pollen calendars and related information sites on the Internet can show how high the exposure is in certain regions. In the case of an allergy to house dust mites, it is possible to reduce the burden in the household somewhat, for example, by regular cleaning, mite-proof bedding, and the removal of dust traps.

Medication:

Antihistamines or cortisone preparations are often used, especially for allergic rhinitis and allergic conjunctivitis. These drugs are available as tablets, nasal spray, or injections. Cortisone ointments or creams are also used for allergic skin reactions.
Hyposensitization (specific immunotherapy): In this treatment, similar to vaccination, low doses of the allergen are regularly injected under the skin or given as tablets or drops under the tongue. Hyposensitization lasts about 3 to 5 years. It is mainly offered for allergies to pollen, dust mites, and insect venom.

So far, there is no evidence that herbal or homeopathic remedies and acupuncture can help with allergies.

Further information
Many research groups are trying to better understand the interplay between the immune system and environmental influences to derive new ideas for the prevention and treatment of allergies.

The family doctor’s office is usually the first place to go when sick or need medical advice for a health problem. We provide information on finding the proper practice, how best to prepare for a visit to the doctor and what is essential when doing so.

Genetic predisposition

The more family members are allergy sufferers, the greater the risk of developing allergic disease children in this family. Children have the highest risk if both parents are affected: They develop allergic symptoms in 50-70%, especially if they suffer from the same allergic disease. On the other hand, if the parents do not suffer from allergies, the risk of disease for the child (according to the Allergy and Asthma Association) is 15%.

Hay fever

Without therapy, hay fever can cause a floor change from the upper respiratory tract (nose) to the lower (bronchi). Thus, at least 30% of people who have hay fever but do not receive specific treatment (hyposensitization) sooner or later also develop asthmatic symptoms. Therefore, hay fever should not be trivialized and should be treated. However, it is also imperative to take precautionary measures.

Excessive hygiene

In the countryside, only about half as many children suffer from hay fever (about 4%) and asthma as in the city (about 10% with hay fever and 6% with asthma). In particular, children who live on a farm from birth or as early as possible (before they reach the age of two) suffer from allergies much less frequently than city children (exception: neurodermatitis is equally common). Moreover, those children whose mothers already worked daily in the barn during pregnancy are particularly well protected against asthma and hay fever.

This difference is apparently that children growing up on the farm come into contact with more germs and can thus build up better immune protection than in the city. Also, compared to children who live in the same village but not on a farm, farm children are about one-third less likely to develop allergic hypersensitivity. Contact with bacteria (or with the bacterial component endotoxin) in childhood possibly causes the immune system to tolerate allergens better. However, it is still unclear exactly how this tolerance effect works.

Conversely, excessive hygiene can promote allergies, such as the excessive use of cleaning agents and disinfectants when cleaning the house (“cleaning mania”). In addition, pregnant women who consistently try to avoid possible allergens are also more likely to promote an allergy in their child to the substances they avoid. These results support the so-called hygiene hypothesis, which states that allergies are increasing because people nowadays come into much less contact with bacteria than in the past. Therefore, in an increasingly sterile world, the immune system lacks “real enemies.” This may be the reason why it starts its self-damaging defensive fights against substances that are harmless. However, this should not be a reason to neglect hygiene or give up vaccination completely.

Air pollution

Increased exposure to fine dust (for example, car and industrial exhaust fumes, cigarette smoke, heating systems, etc.) can aggravate existing allergies. The exact mechanism is still unclear, but ultrafine particles can certainly penetrate particularly far into the deeper sections of the lungs, settle there and cause inflammation. For example, a study in Japan has shown that the frequency of hay fever increases the closer those affected live to a busy road – with correspondingly high levels of particulate matter.
Environmental pollutants (such as nitrogen oxides, soot particles from diesel exhaust, ozone, or cigarette smoke) have been shown to increase the respiratory mucosa’s permeability to allergens and influence the formation of allergy-causing Ig E antibodies. It is therefore thought that they may also promote the development of allergy.

Smoking

If the mother or grandmother were a smoker, the children or grandchildren are more likely to develop allergies. Children (especially girls) whose mothers smoke during pregnancy are at particular risk of developing asthma: Their risk of asthma as adults is increased by 60%. However, if the mother stops smoking during pregnancy, there is no increased risk. If, in addition to the mother, the grandmother had also smoked during her pregnancy, the asthma risk of her adult grandchildren is even more than doubled. If the parents did not smoke during pregnancy but did smoke during the first years of their child’s life, their sons, in particular, tend to develop bronchial asthma or chronic bronchitis in adulthood. Cigarette smoke is thought to cause gene changes that damage the immune system.