Allergy – causes and symptoms, how to treat allergy?

When we talk about allergies, we often don't realize that it's currently one of the most common diseases in the world. According to research, approximately 40% of us suffer from them, and the number of patients continues to grow. Therefore, it's worth knowing what allergies are, why we suffer from them, and whether they can be cured

Allergy and allergens

Today, allergy is defined as a disease that develops due to an erroneous immune system response to substances that are typically harmless. The body's response is triggered by allergens, small, primarily protein-based, particles .
The problem, however, is that almost any substance in the human environment can be an allergen. Correctly identifying them presents the greatest challenge for doctors.

What are the types of allergies?

Allergens can be divided into at least several types. Based on their mode of contact with the body, allergens are most commonly divided into inhalant and food allergens. Additionally, it's worth distinguishing contact allergens and those found in insect venoms and medications.

· Inhalant allergens

They can be found, for example, in dust mites , pollen, or mold spores. Animal allergens are also common in this group. They enter our bodies through the air we inhale. Once they reach the surface of the nose or throat, they can transfer allergens, allowing them to penetrate the mucous membrane and trigger a reaction.

Food allergens

Food allergens are natural substances, occurring primarily in the form of plant and animal proteins. They have been found in all food groups. The main ones include cow's milk , egg whites, soy, peanuts, cereals containing gluten, meat, seafood, and fish. Allergens can also be found in food additives, such as preservatives, colorings, and flavor enhancers.

Contact allergens

When we speak of contact allergens, we mean chemical compounds, most of which are haptens. These substances become full-fledged allergens only after binding to epidermal proteins. Upon direct contact with the skin, they cause various types of irritation.
Although approximately 4,000 chemical substances are known to have allergenic properties, the most common allergens in this group are metals, preservatives, plastics, and fragrances.

· Insect venoms

In Central Europe, most insect venom allergies are caused by honeybees, and less frequently by wasps, hornets, or bumblebees. Beekeepers are particularly vulnerable to stings due to their work.
Not every reaction to an insect sting indicates an allergy and requires medical attention. Normal symptoms include redness, swelling, and pain at the sting site, lasting up to 24 hours. If these symptoms are accompanied by skin reactions (swelling, itching, hives, and angioedema), respiratory reactions (cough, shortness of breath), digestive reactions (abdominal pain, diarrhea), and cardiovascular reactions (low blood pressure, heart rhythm disturbances), then it can be assumed that an insect venom allergy is present.

Allergens in medicines

Virtually all known medicinal substances can cause allergic reactions, although some are more common. Drugs that are more likely to cause allergic reactions include penicillin, amoxicillin, and various nonsteroidal anti-inflammatory drugs (NSAIDs), such as metamizole, tramadol, and others.

Causes of allergies, are genes to blame?

Scientists have been trying for years to answer the question of what causes allergies and whether genes play a role in their development. Put simply, do we inherit allergies from our parents? Researchers believe we don't inherit the disease itself, but we do inherit a certain tendency to develop it. What does this mean? Statistically, the probability of an allergy developing in a child of healthy parents is estimated at 15 percent. If one parent has an allergy, the risk increases to 30-40 percent. If both parents have allergies, the probability of the child is estimated at 60-80 percent.

Scientists emphasize, however, that environmental factors have a greater impact on the development of allergic diseases. These include changes in lifestyle, the type of food consumed, exposure to secondhand smoke, and very likely environmental pollution, excessive hygiene, and excessive use of antibiotics.

Allergy symptoms

It's worth noting right away that an allergy isn't the same as a sensitization. We only talk about it when the allergic person also experiences symptoms. So what symptoms might suggest an allergy?

The most common allergy symptoms include: runny nose, sneezing, nasal congestion and itching, watery and red eyes, conjunctivitis, rash, severe itching and dry skin, shortness of breath, wheezing, itching and burning of the lips and palate, nausea, vomiting, abdominal pain, and diarrhea. Depending on the type of allergy, only some of the above symptoms may be present.

Allergies can sometimes also manifest as anaphylactic shock, which is a life-threatening condition characterized by a drop in blood pressure, loss of consciousness, and shortness of breath.

Cross-reactions

We start thinking about them when allergy symptoms appear after contact with an allergen to which we were not originally allergic. It's possible, for example, to have a diagnosed allergy to birch pollen, but experience symptoms after eating an apple. In such a situation , a cross-reaction can occur, meaning our immune system misidentifies the allergen. Why does this happen? Because many allergens have a similar structure. If the similarity exceeds 70%, then a cross-reaction is highly likely.
Interestingly, such reactions are not uncommon. It turns out that up to 60% of food allergy symptoms are not caused by the food we ate, but may be related to pollen hypersensitivity.
Therefore, it's worth knowing which allergens most often cross-react. This type of reaction often occurs among:

• pollen and food, e.g. people allergic to birch pollen may experience symptoms after eating apples, cherries, peaches, pears, parsley, celery or almonds
• latex and fruit
• cat allergens and pork
• house dust mites and seafood, especially shrimp

Methods of diagnosing allergies

Making a proper diagnosis of allergies is often challenging. Identifying the substance causing the allergy is crucial. Diagnosis begins with a visit to the doctor. The specialist will conduct a thorough interview with the patient, asking about their symptoms, family history of allergies, and also about their lifestyle, meals, and leisure activities. The information gathered will serve as the basis for further diagnosis.

If the doctor suspects an allergy, he or she will order appropriate tests.

The tests ordered may include:

• Skin prick tests – these are typically performed on the skin of the forearms or back. During the test, a drop of alFergen solution is placed on the skin. The person performing the test (usually a nurse) then pricks the skin with a special lancet through the drop of allergen. Results are read after several minutes for skin prick tests and after 48 hours for patch tests.
• Blood tests – performed by drawing a small amount of blood from the patient. They involve determining the concentration of E antibodies in the serum against specific allergens. Blood tests utilize allergen panels (e.g. inhalant , food, pediatric , atopic , or respiratory). Multiplex tests can also be used, which allow for the detection of E antibodies against nearly 300 molecules and allergens in a single test ( Alex2 test ). Importantly, molecular diagnostics allows doctors to expedite diagnosis and assess the possibility of severe allergic reactions and cross-reactions. This type of diagnostics is also helpful in qualifying patients for desensitization (immunotherapy).

• Provocation tests – these tests use natural allergens, such as food. A small amount of the product is administered to the patient and the symptoms are observed. Importantly, these tests are conducted under medical supervision, most often in a hospital.

Can allergies be cured? Allergy medications 

Once we know we have an allergy, we often have to make quite radical changes to our lives. The most important step is to eliminate the allergen from our diet or environment. If this is impossible, we should try to limit our exposure to the allergen as much as possible. If symptoms worsen, a doctor will prescribe appropriate medications, most often glucocorticosteroids and antihistamines.

However, the only method for treating the causes of allergies is immunotherapy. It involves the safe administration of an extract containing the allergens to which the patient is allergic. This allows the immune system to learn to tolerate these substances. Immunotherapy is always conducted under the supervision of an experienced specialist. This type of therapy typically lasts 3 to 5 years.

Not every allergy sufferer can benefit from immunotherapy. In Poland, this method can be used to treat patients allergic to pollen (grass, birch, alder, hazel, mugwort), molds (Alternaria), house dust mites, and insect venoms (wasp, bee). Immunotherapy is less frequently used for animal allergens (cat and dog).

Types of immunotherapy:

• subcutaneous injection involves administering appropriate doses of allergen extract in the form of injections, first weekly and then monthly.
• Sublingual immunotherapy can be administered using drops or tablets. Treatment begins in a specialist's office, and then the patient continues to administer subsequent doses independently at home.

*Journal of Allergy and Clinical Immunology Page: JACI

* World Allergy Organization Website: WAO

* Allergy (European Journal of Allergy and Clinical Immunology) Page: Allergy Journal

* PubMed Website: PubMed

* Centers for Disease Control and Prevention (CDC) - Allergies Website: CDC Allergies

* UpToDate Page: UpToDate

* Current Opinion in Allergy and Clinical Immunology Page: Current Opinion