Allergies are a common cause of illness, affecting all age groups. Allergic diseases can range from mild illness to even life threatening conditions. The underlying problem is with the IgE immunoglobulin which is produced in large amount. We do inhale a number of particles and eat various types of food in a day but usually our body does not react to them. It does not form any antibodies against them. However the case is different in a person who is allergic to something. The body recognizes that allergen (which leads to allergy) and activates the B cell of the immune system. This produces IgE antibodies and leads to what is known as the ‘antigen-antibody’ reaction.
Allergen binds with IgE and this leads to activation of a special type of cells- the mast cells. These cells then release a number of vasoactive mediators which then cause a number of symptoms. The chief mediators of allergy are histamine, leukotrienes, prostaglandins and thromboxanes. The symptoms can vary raging from simple sneezing to the life threatening, anaphylaxis. They occur immediately after the affected person comes in contact with the allergen. In few patients, the early response is often followed by local inflammation and swelling. This late response is usually due to a number of cells like eosinophils, basophils and macrophages.
More and more people are suffering from allergic diseases all over the world. The exact cause of allergies still remains unknown though various theories have been proposed. Some say that you become more prone to getting allergies if your immune system gets affected by infections in early life. Allergies have often been associated with a family history. It is said that there are genes which make the person susceptible to allergies. So you are basically born with allergy prone genes!
The most common allergic diseases are Urticaria, Atopic dermatitis, Allergic asthma, Drug allergy, Food allergy, Allergic rhinitis, Angioedema and Anaphylaxis. When a patient presents with allergic symptoms, it becomes important for a doctor to identify the allergen. A detailed history is thus extremely important. The allergen which triggers the reaction is often found at patient’s home or work place.
Skin prick tests are often done to diagnose allergic conditions. It is a very specific and sensitive test. Other than this, IgE tests are also done though these are expensive and less specific than the skin tests. Challenge tests are also performed in which the patient’s nose or skin is challenged by the suspected allergen. Blood test will often show an increased level of eosinophils. Measuring the level of mast cell tryptase in blood is also a good test for diagnosing allergies.
People suffering from allergic diseases should avoid exposure to the concerned allergen completely. They should not go to places or eat such food which has the allergen to which they are allergic. The main drugs used for treating allergies are the anti histamines. They block the release of histamine which is one of the most important mediators of allergy. Corticosteroids are also often used. They are quite effective in the management of allergic diseases. Drugs which stabilize the mast cells like sodium cromoglicate are also increasingly being used. They are often used in the management of allergic rhinitis and asthma. Antigen specific immunotherapy involves administration of allergen in dilute form over a long time. ‘Omalizumab’ is an antibody against IgE and prevents its binding to mast cells. It’s used it treating severe form of asthma. Adrenaline is used in emergency conditions like anaphylaxis, a severe systemic allergic reaction.
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