Why Do People Develop Allergies?

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People often wonder why they become allergic.

The arrival of spring coincides with the onset of allergy symptoms. But what exactly is an allergic reaction, and how does it differ from an intolerance? How does the allergic response occur within the body?

Allergies represent an abnormal and excessive reaction of the immune system to substances that are normally harmless. These substances, called allergens, may be present in the environment, foods, pets, or even medications.

The allergic response occurs in three phases:

Sensitization: During the first encounter with an allergen, the immune system mistakenly recognizes the substance as harmful and produces specific antibodies called Immunoglobulin E (IgE) to combat it. This phase may occur without obvious symptoms.
Activation:
Upon subsequent exposure to the same allergen, the IgE antibodies present on the surface of mast cells and basophils recognize the allergen and trigger an immune response. Mast cells and basophils release histamine and other chemicals into the bloodstream, causing the typical allergy symptoms.
Symptom manifestation : The released substances, such as histamine, cause tissue inflammation and result in allergic symptoms, which may include itching, skin rashes, nasal congestion, sneezing, coughing, breathing difficulties, nausea, vomiting, diarrhea, or, in severe cases, anaphylaxis.

Allergic manifestations vary widely between individuals and depend on the allergen involved as well as individual sensitivity. However, common manifestations include:

Skin Reactions – Common symptoms include rashes, itching, hives, and swelling. These may appear on various parts of the body, often following contact with the allergen.
Respiratory Issues – Allergies can affect the respiratory tract, causing symptoms such as coughing, sneezing, nasal congestion, difficulty breathing, and wheezing. These symptoms are typical in seasonal allergies such as pollen or dust mites.
Gastrointestinal Symptoms – Some individuals experience digestive issues such as nausea, vomiting, diarrhea, or abdominal pain in response to food allergens.
Anaphylactic Reactions – In more severe cases, an allergy may trigger anaphylaxis, a serious and potentially life-threatening systemic immune response. Symptoms of anaphylaxis include throat swelling, difficulty breathing, low blood pressure, rapid heartbeat, dizziness, and loss of consciousness. Immediate medical intervention is required.

Both allergies and intolerances are bodily responses to specific substances, but there are important differences:

Allergy involves the immune system and presents with a wide range of symptoms, from mild to severe. Allergies can be diagnosed through skin tests, blood tests measuring specific IgE antibodies, or, in some cases, through clinical examinations following controlled exposure to the allergen..
Intolerance does not involve the immune system and is often the result of metabolic or digestive problems. Intolerances may cause symptoms primarily related to the digestive system, such as bloating, abdominal cramps, diarrhea, or constipation, and are more difficult to diagnose as they do not involve measurable immune responses. Diagnosis often relies on observing symptoms in relation to food or substance intake, along with dietary elimination and empirical testing.