Allergy is a conditions where your body abnormally reacts to foreign substances that normally should not produce any reaction. These substances are called allergens. Your immune system, which is responsible for protection of the body against external agents, recognizes these allergens as “invaders” and produce proteins (antibodies) to neutralize these agents. When these antibodies combine with the allergen, an allergic reaction is produced which can manifest as a skin rash to life threatening cardiovascular collapse. Common allergens are pollens, grass, house mites, animal danders, molds, latex, certain food (peanut, lactose in the milk) etc. Both the genetic makeup of the person and environmental factors are responsible for triggering the allergic reaction. People who suffer from allergies are usually sensitive to more than one allergens.
Allergy manifests as different symptoms based on the organs ( nose, throat, lungs, sinuses, ear, skin and gastrointestinal tract) involved. Signs and Symptoms range from mild symptoms of itchiness, rash, runny nose watery/red eyes to a life threatening reaction called anaphylaxis. Moderately severe symptoms include swelling of airway causing breathing difficulties.
Types of Allergic Diseases
Allergic rhinitis, also called hay fever, mostly occurs during spring and fall due to airborne pollens. It is also called seasonal rhinitis. Allergic rhinitis can occur in response to allergens that are present throughout the year like animal dander, proteins derived from cockroaches, mold spores and dust. This is called perennial allergic rhinitis. Symptoms include sneezing, stuffy or running nose, obstruction of the nasal passage, itching in the conjunctiva, nasal mucosa, pharynx and roof of the mouth. In susceptible people, symptoms generally appear before the fourth decade of life and tend to diminish gradually with aging.
Also known as hives, urticaria is characterized by red bumps on the skin of varying sizes that occur in groups. These involve the upper part of the skin and may be associated with swelling and itching. Urticaria is often associated with swelling. Atopic dermatitis or eczema is another skin manifestation of allergy with symptoms like itching, reddening and peeling of the skin. More than half of the people with atopic dermatitis have been found to develop asthma.
When eye is exposed to specific allergic agents, it shows the symptoms of allergic conjunctivitis like itching, reddening, swelling of the conjunctiva and watering of the eye.
Allergy plays a significant role in pathogenesis and manifestation of disease. Details discussed elsewhere.
Food allergy occurs when the immune system of the body recognizes a particular food protein as an allergen. Even tiny amount of the food is enough to trigger the allergic reaction. Most common type of food items that trigger allergic reaction are cow’s milk, peanuts, egg protein, wheat, soy, fish, shellfish and tree nuts.
Sinuses are hollow cavities within the face around our eyes and behind the nose. Allergy can trigger inflammation in these sinuses which produces nasal congestion, cough, fever and thick, dirty nasal discharge. This condition is known as allergic rhino-sinusitis. People with asthma and allergic rhinitis are more likely to suffer from sinusitis because of frequent involvement of airways.
Anaphylaxis is a severe form of allergic reaction which is life threatening. It can affect more than one body part at the same time. Symptoms include red itchy rash, lightheadedness, difficulty in breathing, tightness in the throat and chest, anxiety, abdominal cramps, vomiting and diarrhea. Anaphylactic reaction can manifest as shock when there is sudden fall in the blood pressure which leads to loss of consciousness. Agents known to cause anaphylaxis are food items, insect bites, wasp sting, latex and various types of drugs. Since it is a life threatening condition, anaphylaxis requires immediate medical attention which includes maintenance of airway, breathing and circulation as first aid and injection of epinephrine as treatment. Urgent hospital admission is required when symptoms of anaphylaxis are seen. If not treated on time, anaphylactic reactions can also be fatal due to respiratory failure.
Diagnosis and Treatment
A thorough medical history and physical examination is required to identify allergy. Family history of allergy and history of environmental exposure to allergen is equally important. Allergy skin testing or patch testing with blood examination is also performed in order to determine the type of allergic agent involved.
Once a specific allergen is identified, you should try to avoid exposure to the offending agents. Drugs such as antihistamines and decongestants in form of tablets can be prescribed in order to relieve the allergy symptoms. Topical nasal sprays are helpful in treating nasal symptoms. Severe symptoms not controlled by avoidance and medications can be sometimes treated by immunotherapy called “allergy shots”. In this treatment, doctor gives you a series of injection of the allergen extract under your skin over a long period of time so that you develop tolerance to the allergen. If you had an anaphylactic reaction before, your doctor will ask you to carry an “epi-pen” that contains epinephrine that you can inject under the skin when you feel you might be having an anaphylaxis. Although there is no cure for allergy once diagnosed, following the advice from the physician and appropriate modification in lifestyle can protect from allergic reactions in the future.