Understanding allergies: from symptoms to treatment

Allergies are overreactions of the immune system to substances that are actually harmless, such as pollen, food, or animal dander. They affect millions of people worldwide, and their prevalence continues to rise. Up to 30% of the global population is affected by one or more allergic conditions (AAAAI, 2024). Symptoms range from itching and breathing difficulties to skin reactions, all of which can significantly impact daily life. In this blog, you will learn everything about the causes, diagnosis, treatment options, and prevention of allergies.

Table of Contents

• What is an allergy?
• What causes allergies?
• What are the symptoms?
• How are allergies diagnosed?
• How are allergies treated?
• Summary

What is an allergy?

An allergy is a malfunction of the immune system in which it perceives harmless substances—called allergens—as threats. Allergies develop in two phases:

• Upon first contact with the allergen, the immune system becomes sensitized and produces specific antibodies (IgE).
• Upon repeated exposure, the immune system recognizes the allergen and triggers a defense response. This results in the release of histamine and other chemical messengers, which cause typical allergy symptoms.

Another key feature of allergies is that, unlike infectious diseases, they generally occur without a fever. An allergy is not an infectious disease (NHS, 2023).

Who can be affected by an allergy?

Allergies can affect people of all ages, from infants to seniors. Food allergies are more common in childhood, as the immature immune system reacts more strongly to new substances. Many of these allergies—such as those to milk or eggs—disappear over time, as the immune system learns to tolerate harmless substances. Other allergies, such as hay fever, often persist for life. Allergies can also develop suddenly at any age, even without previous signs.

What causes allergies?

Allergies are triggered by allergens—substances that are usually harmless but are mistakenly classified by the immune system as dangerous. Depending on the allergen, allergies are divided into several categories, including inhalation allergies (e.g., pollen, dust mites), food allergies, contact allergies (e.g., metals), and insect venom allergies. Common allergens include:

• Pollen: grasses, trees, weeds
• House dust mites: mite droppings
• Animal dander: skin particles or saliva
• Foods: e.g., nuts, milk, eggs, soy
• Insect venom: bee or wasp stings
• Mold: airborne spores
• Contact substances: metals (e.g., nickel), latex

Environmental factors such as air pollution or tobacco smoke can also aggravate allergic reactions (Cleveland Clinic, 2022).

Why are some people more sensitive?

The reason some people are more sensitive to allergens lies in a combination of genetic/inherited and environmental factors. Children of allergy sufferers have a significantly increased risk of developing an allergy themselves. In addition, environmental factors such as air pollution or contact with harmful substances can promote immune system sensitization. A weakened immune defense, smoking, or frequent infections during childhood are also considered risk factors for the development of allergies (Mayo Clinic, 2024).

What are the symptoms?

The symptoms of an allergy vary depending on the type of allergy and the affected area of the body. Inhalation allergies often affect the airways and eyes, contact allergies affect the skin, food allergies affect the gastrointestinal tract, and insect venom allergies can affect both the skin and circulatory system simultaneously. Common symptoms by which you can recognize an allergy include:

• Respiratory system: Sneezing, blocked or runny nose, coughing, shortness of breath
• Skin: Redness, itching, hives, eczema (rashes)
• Eyes: Itching, redness, watery eyes
• Gastrointestinal tract: Nausea, vomiting, diarrhea
• Severe reactions: Anaphylaxis with a drop in blood pressure, respiratory arrest, unconsciousness

What happens during an allergic shock (anaphylaxis)?

An allergic shock, also known as anaphylaxis, is an extreme overreaction of the immune system to an allergen. Within minutes, large amounts of histamine are released, leading to a drop in blood pressure, shortness of breath, swelling (e.g., in the throat), and circulatory failure. Without treatment, the condition is life-threatening (NHS, 2023).

How long does an allergic reaction last?

The duration of an allergic reaction varies depending on the trigger and severity. Acute symptoms such as itching, sneezing, or skin rashes can last from minutes to hours. Swelling or inflammation usually refers to skin reactions, such as hives or redness, that occur after contact with the allergen. These typically subside within one to two days but may last longer in the case of strong exposure or without treatment.

How are allergies diagnosed?

Allergies are diagnosed through a combination of medical history, clinical examination, and specific tests:

• Medical history: Recording symptoms, triggers, and family history of allergies.
• Skin tests: A prick test is a skin test in which allergen solutions are applied to the skin and the skin is lightly pricked. After 15–20 minutes, redness or wheals indicate whether sensitization is present.
• Blood tests: These tests measure specific IgE antibodies in the blood that are produced in response to certain allergens. A high level of IgE antibodies indicates that the body is sensitized to an allergen. The higher the level, the stronger the allergic reaction may be.
• Provocation tests: In this test, the allergen is applied directly to the affected area (e.g., nose, eyes) or taken orally to observe the reaction under medical supervision.

In Germany, prick and provocation tests are offered by specialized general practitioners, dermatologists, pulmonologists, or allergy centers. Blood tests can be performed by specialists, regular general practitioners, or at home using self-testing kits (Mayo Clinic, 2024).

When should you see a doctor?

You should see a doctor if allergy symptoms such as frequent sneezing, itching, rashes, or breathing difficulties occur, especially if they affect your quality of life. In the case of severe reactions like shortness of breath, significant swelling, or signs of an allergic shock, immediate medical attention is necessary.

How are allergies treated?

Treatment strategies aim to address different goals depending on the urgency and severity of symptoms. They include acute symptom relief, long-term quality of life improvement, and emergency interventions:

• Short-term measures: The goal is to quickly relieve acute symptoms such as itching, sneezing, rashes, or mucous membrane irritation. Antihistamines block histamine, while nasal sprays and eye drops provide localized relief. At the same time, avoiding allergens is essential to minimize the risk of symptoms.
• Long-term strategies: The focus here is on sustained control. Desensitization (specific immunotherapy) involves regular administration of increasing doses of the allergen under careful monitoring. This trains the immune system to become less sensitive to the allergen, thereby reducing allergy symptoms in the long term.
• Emergency care: In emergencies, immediate medical assistance is crucial. Many allergy sufferers carry an emergency kit with an epinephrine auto-injector, antihistamines, and corticosteroids to respond quickly in critical situations.

Source: Mayo Clinic, 2024

How can allergies be prevented?

Allergies cannot always be completely prevented, but targeted measures can significantly reduce the risk. Key strategies include reducing allergen exposure, maintaining balanced hygiene, adopting healthy lifestyle habits, and early prevention—especially in children.

• Reduce allergen exposure: Regular ventilation, the use of air purifiers, and frequent cleaning can lower the risk of developing allergies.
• Breastfeeding for at least 6 months: Breast milk strengthens the immune system and reduces the likelihood of developing allergies.
• Promote a balanced diet: A varied diet supports the gut microbiome and boosts immune health.
• Avoid delaying the introduction of potential allergens: Introduce foods like peanuts or eggs gradually and age-appropriately to prevent hypersensitivity.
• Avoid smoking and air pollutants: Tobacco smoke and environmental toxins weaken the immune system and increase the likelihood of allergies.
• Strengthen the immune system: Regular physical activity, fresh air, and stress reduction help improve the body’s natural defenses.
• Early treatment: Treat initial symptoms promptly to prevent chronic conditions and further sensitization.

Source: AAFA, 2025

Summary

Allergies are immune system overreactions to substances that are actually harmless, such as pollen, food, or animal dander. They can cause a wide range of symptoms, from itching and rashes to breathing difficulties or severe reactions like anaphylaxis. Causes include genetic predisposition, environmental factors, and immune system sensitization. Diagnosis involves taking a medical history, skin and blood testing, and provocation tests. Treatment includes acute symptom relief with antihistamines, long-term strategies such as desensitization, and emergency care with epinephrine.