What is allergy ?
An allergy is an abnormal sensitivity to an allergen that is inhaled, eaten or touched that most other people can tolerate with no trouble. Allergies are Over-reactions to substances one's immune system considers harmful.

What are common allergens?
There are two types of Allergens:-

• Seasonal : These are mainly outdoor allergens and include pollens from grasses, trees and weeds, and also some moulds.
• Parennial : These are usually indoor allergens, and cause symptoms all year round. The commonest is the house dust mite. These reside in nests such as carpets, bedding and upholstered furniture. They are triggers for perennial rhinitis and allergic asthma. Other perennial allergens include domestic pets, especially cats.
  
  Food Allergens : There is an increasing evidence that different foods play significant roles in manifesting allergies. They can manifest as itching, Urticaria, Swelling of mouth. Throat obstruction, Respiratory difficulty etc. The common foods are milk, eggs, peanuts & other nuts, wheat, soya, fish etc.
  
  Drugs : Any drug can cause allergic reactions but aspirin & other anti-inflammatory drugs as well as antibiotics lie penicillin, sulphonamides account for most of the allergic reactions due to drugs.
  
  Insects : Each year about 40 peoples die in the USA from Anaphylaxis to insect (bee, wasp & fire ants venom) sting.

Is allergy inherited ?
If both parents have respiratory allergies then risk that their offspring's develop an allergy goes up to 80 %.
The increased tendency of some families to develop allergy sensitization is termed as atopy. There are three classical kinds of atopy: Atopic dermatitis (eczema), Hay fever (seasonal allergic rhinitis) and allergic asthma.

Do children out grow allergies ?
Sometimes, Food allergies are more likely to be outgrown than inhalant allergies. Food allergy is much more common in children than adults.

Common allergic manifestation.

• Asthma.
• Allergic Rhinitis (Hay fever)
• Atopic Eczema
• Contact dermatitis
• Urticaria
• Food Allergy
• Allergic Conjunctivitis (Itchy eyes)
• Wasp venom Allergy
• Drug allergy

How is allergy diagnosed ?
A good medical history is usually the basis for the diagnosis of any allergy. Knowledge of the family history of allergic problem is very helpful. It may take some good detective work by doing various tests to figure out exactly what the likely allergen is.

Following tests are available to find out the possible allergens :

• Skin prick test .
• RAST.
• IgE.
• AEC (absolute Eosinophil count).
• Nitric oxide estimation in exhaled air as a marker of allergic inflammation.
• Provocation tests. (for food and drug allergy).
• Skin Patch testing. (for contact allergy).
• Skin Scratch tests.(mainly for drug allergy).
• Drug allergy.

Skin Prick Testing : It is the oldest allergy test firstly performed in 1865 by Dr. Charles Blackley in Manchester, England. Standardized glycerinated extracts of various allergens are used which are highly accurate in its results to confirm which allergen are highly accurate in its results to confirm which allergen is responsible. A diluted extract of each kind of allergen is pricked into the skin of the forearm or on the back. With a positive reaction; a small raised, reddened area with surrounding flush (called a wheal & flare) will appear at the test site. The results are measured after 15 to 20 minutes.
Blood Tests : Diagnostic tests can be done using a blood sample from the patient to detect levels of IgE antibody to particular allergens. These tests are performed when the entire body is covered with eczema or if the patient is on antihistamines which can interfere with skin prick test results. These are also done in children where skin prick tests are not feasible.

How are allergy treated ?

• The diagnosis should ideally be confirmed, to determine the exact source of the allergy before commencing treatment.
• Once the allergens positively is established, its clinical significance is correlated.
• The best way to treat allergies is to avoid exposure to allergens in the first place, but this is not a practical solution generally.
• Many treatments are available to relieve symptoms, ranging from Over-the-counter antihistamines to potent anti-inflammatory drugs like steroids.
• Immunotherapy, is an another method of treating allergies which is effective by producing blocking antibodies to counteract the allergy manifesting antibodies.

Immunotherapy
ALLERGY SHOTS IS THE TERM OFTEN USED FOR ALLEERGEN IMMUNOTHERAPY TREATMENT OR ALLERGY VACCINATION.

HOW DOES THE TREATMENT WORK?
If you are allergic to a substance such as pollen, you will not over come your allergy by repeatedly inhaling pollen into your nose or lungs. So how can increasing your exposure to the substance that trigger your allergies – such as pollen or mite allergen help you?
Allergen immunotherapy works like a vaccination. Through your body’s exposure to small injected amount of a particular allergen, in gradually increasing doses, your body builds an immunity to the allergen to which your body is allergic. This means that when you encounter these allergens in the future, you will have a reduced or very minor allergic response and fewer symptoms.
At the beginning of allergen immunotherapy, the first injection consist of a small amount of the least concentrated vaccine each week the patient receives a slightly more concentrated allergen vaccine injection. The rate of which this degree of sensitivity. Usually the patient will reach a top (maintenance) dose about four to six months after injections are begun. The initial dose is begun every month, and later the interval usually is extended to every three to four weeks for maintenance.
If you begin allergen immunotherapy treatment, it is very important to continue your injection on a regular basis until the treatment is discontinued. Otherwise, the treatment will not be beneficial.
Generally patient’s receive injections for three to five years or longer. After that, their sensitivity to the particular allergen to which they are allergic is reduced, often for years, following discontinuation of therapy. This can mean, for instance, that they may be able to tolerate the outdoors during specific pollinating seasons with out experiencing symptoms.
Allergen immunotherapy works by altering the abnormal immune response that cause allergy. Protective antibodies, similar to those made in response to other vaccine, play a role in the beneficial results or allergen injection therapy.

Benefits
Allergen immunotherapy treatment is considered when allergy symptoms are moderate to sever, occur throughout most of the year, do not respond adequately to medications, and are triggered by allergens not easily avoided, such as pollens or house dust mite allergens.
For example, if your are extremely allergic to both grass and pollens, you may experience intolerable symptoms such as sneezing, a running nose, and itchy, red eyes and nose during the spring and fall. It is impossible or at least impractical, for you to completely avoid these common, airborne allergens. Although air conditioning will help decrease indoor pollen exposure, and medication may be helpful, you may find you still experience symptoms for prolonged periods at those times for the year.
For such patient, allergen immunotherapy with grass allergens will provide significant relief.

Potential side effects As you can see, allergen immunotherapy can be beneficial for many allergic patients. However there are also some drawbacks. Some patients may find repeated visit to their allergist (or other physician who administers their injections) to be inconvenient. After you receive each injection, your allergist or other physician administering your injection will require that you remain in the clinic for 20mts or longer so the staff can monitor you. During treatment some patients develop swelling at the site of the injection. When these are large, they are called “local reactions”, oral antihistamines, ice packs and adjustment of the dose or vaccine resolves these reactions. Rarely, a patient may have a more serious allergic reaction, resulting in asthma symptoms or anaphylaxis. Asthma symptoms include cough, wheezing and shortness or breath. Symptoms of an anaphylactic reaction can include sneezing, watery nasal discharge, itchy eyes, swelling in the throat, wheezing or a sensation of tightness in the chest, nausea, dizziness or the symptoms. Such reactions require immediate treatment. If not appropriately treated, these reactions may become serious. Your allergist is trained to monitor for such reactions-that is why your are asked to remain in the clinic for 20 mts or more after your injection.

What exactly is allergens specific immunotherapy?
It is the process of administering increasing amount of allergens by subcutaneous for which a patient is found to be allergic. It eventually builds tolerance to these allergens substances and prevent them causing symptoms.

How does immunotherapy work?
The exact mechanism by which immunotherapy switches off allergies is uncertain. It was hypothesized that specific "IgE blocking" antibodies were produced during successful immunotherapy in specific IgE was followed by an IgE fall with compensatory rise in IgE (a blocking antibody)

Is Immunotherapy a "cure"?
Immunotherapy may not be cure but can significantly lessen symptoms to different degrees to substances contained in the immunotherapy. Studies showing the effectiveness of immunotherapy show that roughly 8 out of 10 patients benefit from immunotherapy.
Generally the period to have immunotherapy injections may vary from 3 months to 1 year but in some cases it might need to be given up to 3 to years for long-term benefit. Improvement in symptoms is usually observed in 6 months to 1 year of immunotherapy. Total period of immunotherapy may vary from 3 months to a year.