ALLERGY AND IMMUNOLOGY

The word "Allergy" takes his significance in two greeks words: Allos: "different" and Ergon: "effect".

An allergy is a sensitivity to a certain substance which, in similar quantity, is tolerated by non-allergic people. The allergen is the specific protein substance that a person is allergic to. The presence of this allergen in the body causes a series of chemical reactions in the immune system which result in individual signs & symptoms.

Allergies can affect anyone, regardless of age, gender, race, or socioeconomic class. Generally, allergies are more common in children, however, a first-time occurrence can happen at any age, or recur after many years of remission

The allergic reaction in the immune system can be caused by:

• Ingestants: substances that enter the body by mouth
• Inhalants: the allergen is breathed in through the nose or mouth
• Contact Allergies: enter the body through the skin
• Other Factors: may aggravate the allergy

Ingestants

• Two main ingestants are:
• food
• drugs

Inhalants

Inhalants are protein substances breathed in through the nose or mouth. There are different kinds of inhalant allergens:

• Pollens
• Molds
• Animal Secretions
• House Dust Mite

Contact Allergies

These allergens enter the body through the skin. They include:

• powders
• lotions
• some metals such as cheap jewellery, jean snaps and clips on bras
• latex

Other Factors

Non-specific factors that may aggravate an allergy include:

• weather changes
• heat
• cold
• humidity
• barometric weather changes
• infections
• second hand smoke

Signs and Symptoms of Allergies

There are a wide range of potential signs and symptoms of allergies, and they depend on many factors:

• type of allergy
• level of exposure
• individual's reaction

Because these signs and symptoms may indicate the presence of another disease rather than an allergy, they should be investigated by your physician.

The main symptoms are:

• itchy, watery eyes
• itchy, runny nose

Some other signs and symptoms are:

• itching
• eczema
• hives
• dark circles under and around the eyes
• recurring headache
• shortness of breath
• wheeze
• cough
• diarrhoea
• stomach cramps

How are allergies diagnosed?

• Diagnosis of allergy to airborne substances is made based upon:
• Symptoms/medical history
• Physical exam
• Skin tests (injection of various antigens just under the skin, to test for sensitivity)
• Less commonly, blood tests (to detect antibodies against particular antigens)
• Diagnosis of food allergy is made based upon:
• Symptoms/medical history
• Diet diary (record of foods eaten and occurrence of symptoms)
• Elimination diet (under the supervisions of a health care provider, tracking the occurrence of symptoms, as specific foods are systematically eliminated from and re-introduced into the diet)
• Skin tests and/or blood tests

There are 3 main steps in the treatment of allergies:

1. Avoiding contact with the specific allergen.
2. Medication - drugs can be taken for the target organ affected.
3. Allergy shots, or immunotherapy (regular injections of the allergen in order to desensitize the body), are appropriate in some, but not all, allergy conditions.

• Medications for allergies include:
• Antihistamines, either over-the-counter or prescription
• Nasal sprays
• For severe (anaphylactic) food allergies: prescription adrenaline (epinephrine), to be self-injected in the event of inadvertent ingestion of an allergenic food

Skin/ Blood test for Allergy

Allergists have tools at their disposal to identify what substances cause your allergies and which of these substances may trigger an asthma attack. Perhaps the two most common of these tools are a blood test (called RAST) to determine levels of IgE antibodies, and skin tests to determine what substances can trigger allergies and allergy-triggered asthma.

Skin tests are more sensitive in predicting an allergy than the RAST test and cost less. A blood test and skin tests to determine levels of IgE antibodies can be an important tool in identifying allergies. If these tests detect elevated levels of IgE antibodies in the blood, an allergic condition is likely. For some people who also have documented asthma, high levels of IgE in the blood may indicate the need for aggressive use of asthma medications to lower the chance of experiencing severe asthma attacks. Whether you or your family member has asthma, if these tests determine high IgE levels, your doctor will want to perform other tests to confirm these results and determine what substances can trigger an allergic reaction.

When performing skin tests, doctors use diluted liquids made from the actual allergens. Skin tests can check for allergies to various types of pollens, molds, foods, and animal danders. The allergist applies these liquid allergens by pricking the surface of the skin and dropping a tiny amount of the allergen extract into the scratch mark. After 15 to 20 minutes, he or she will check to see if any of the allergens cause a small "mosquito-bite" type of allergic reaction. What the allergist is looking for is a kind of rash or hive that doctors call a wheal. If you have allergies, you have IgE antibodies that recognize and react to any of the substances that causes a wheal. However, only with a careful history taken by the allergist can your doctor decide what substances trigger your disease.