What is an allergic reaction?

Normally, the immune system functions as the body’s defense against invading germs such as bacteria and viruses. In most allergic reactions, however, the immune system is responding to a false alarm. When an allergic person first comes into contact with an allergen, the immune system treats the allergen as an invader and gets ready to attack.

The immune system does this by generating large amounts of a type of antibody called immunoglobulin E, or IgE. Each IgE antibody is specific for one particular substance. In the case of pollen allergy, each antibody is specific for one type of pollen. For example, the immune system may produce one type of antibody to react against oak pollen and another against ragweed pollen.

The IgE molecules are special because IgE is the only type of antibody that attaches tightly to the body’s mast cells, which are tissue cells, and to basophils, which are blood cells. When the allergen next encounters its specific IgE, it attaches to the antibody like a key fitting into a lock. This action signals the cell to which the IgE is attached to release (and, in some cases, to produce) powerful chemicals like histamine, which cause inflammation. These chemicals act on tissues in various parts of the body, such as the respiratory system, and cause the symptoms of allergy.

Allergy

An allergy is an abnormal or exaggerated response of a person’s immune system to a substance in their environment which is generally a harmless substance. This substance (which can be, for example, animal dander, certain foods, dust, mold, and/or pollen) is called an allergen. The outward bodily manifestation of this abnormal or exaggerated response of a person’s immune system is commonly referred to as an allergic reaction.

The following conditions are often associated with or caused by your allergies:

Anaphylaxis

Anaphylaxis is a severe and potentially life threatening allergic reaction and can occur in response to any allergen. The medical definition of anaphylaxis is a rapidly developing, systemic allergic reaction that is mediated by an antibody known as immunoglobulin E (IgE). IgE is the “mediator” between the allergen attacking the body and the mast cell that the IgE is attached to, which triggers the release of histamine.

Allergic Conjunctivitis

There exists a clear, thin membrane called the conjunctiva which lines your eyeball and the inside of your eyelid. If something, such as an allergen, irritates this covering, your eyes may become red and swollen and may also itch, hurt, water or tear; the medical name for this condition is allergic conjunctivitis. Someone with allergic conjunctivitis (conjunctivitis caused by allergies) usually also has allergic rhinitis, or nasal symptoms, as well. Conjunctivitis can also be non-allergic caused by bacteria or viral infection, and is commonly known as “pink eye.

Allergic Rhinitis

Allergic rhinitis is an inflammation of the nasal passages caused by airborne allergens (such as dust, dander, or plant pollens). Allergic rhinitis is characterized common cold-like symptoms such as sneezing, runny nose and itching eyes, and is commonly known as hay fever.

Asthma

Asthma is a chronic, inflammatory lung disorder of the airways with 2 main components: constriction (the tightening of the muscles around the airways) and inflammation (the swelling of the airways). Asthma is characterized by recurrent breathing problems and acute episodic attacks of shortness of breath, wheezing, chest tightness and coughing.

Nasal Polyps

Nasal polyps are non cancerous (benign) growths that develop on the lining of your nose and/or sinuses. Symptoms include difficulty breathing through your nose, and runny nose.

Sinusitis

Your sinuses are air-filled, hollow cavities around your nose, throat and nasal passages. When you get sinusitis, these passages become inflamed, and fluid accumulates and interferes with normal drainage of mucus in the sinuses. Untreated sinusitis may develop into a chronic condition. When symptoms last less than 4 weeks, it is considered “acute sinusitis.” When symptoms are recurring or last longer than 12 weeks consecutively, then it is considered “chronic sinusitis.” A common cause of sinusitis is allergies and common symptoms include facial pain and pressure especially in the cheeks, forehead, nose, temples, and behind the eyes, difficulty breathing through the nose, and nasal obstruction or congestion.