Allergies: An Introduction

Allergies are a type of hypersensitivity that is mediated by IgE antibodies.

Basically, a person is exposed to a substance by either direct contact, injecting, inhaling or ingesting. If the substance elicits an immune response then it is known as an allergen. There are many, many different allergens known.

Some of the common allergens are plant pollen from trees, grasses and other plants. Food, especially nuts, peanuts, seafood and milk. Also, mold spores can cause lots of problems for many people. Even drugs such as antibiotics can result in an allergic reaction. Stings from insects such as bees and wasps and the chemicals in poison ivy and poison sumac. Other common triggers of allergies are cats, dogs, roaches and dust mites.

After exposure to the allergen IgE (immunoglobulin E) antibodies react and lead to the production of histamine and arachidonate by basophils and mast cells. This results in an inflammatory response within only seconds or minues after exposure. The response could be local to a particular part of the body or throughout the body. For most people the symptoms are mild to severe irritation but some cases could result in anaphylactic shock.

Symptoms of Allergies

Symptoms of local allergic reactions include allergic rhinitis, allergic conjunctivitis, asthma and bronchoconstriction and skin problems such as eczema, hives and other rashes and contact dermatitis.

Allergy Tests

The most common test for allergies is a skin test. In this test the skin on either a person's arm or back is divided into little sections with a marker. Then a little bit of each suspected allergen is applied to the appropriate section. It is applied by making a small prick in the skin. If the person is allergic to the substance a red mark or welt will appear.

Allergy Treatment and Medication

Many people get allergy shots, also called immunotherapy, to treat their allergies. Allergy shots are injections of progressively larger doses of the allergen(s) the person reacts too. These shots either make the allergy symptoms less bad or sometimes the person loses their hypersensitivity to the allergen.

There are a number of different medications available to treat allergies. It is important to note that these medications do not cure or make the allergies go away for good, they just reduce or eliminate the symptoms while the medication is being taken. The following are the classes of drugs available for allergies:

- Short-acting antihistamines: These are usually non-prescription and may cause drowsiness. An example that doesn't cause drowsiness is Claritin.

- Longer-acting antihistamines: These usually need a prescription but cause less drowsiness. Examples are Allegra (fexofenadine) and Zyrtec (cetirizine).

- Nasal corticosteroid sprays are also usually prescription only and include fluticasone (Flonase), mometasone (Nasonex) and triamcinolone (Nasacort).

- Cromolyn sodium is also a nasal spray (Nasalcrom). There are also eye drops available for those whose allergies bother their eyes too.

- Leukotriene inhibitors: Singulair (montelukast) is an example and is a prescription medication for asthma and seasonal allergies.

Cause of Allergies

The cause of allergies is still not clear, although genetics may play a role to some degree. One popular theory is called the hygiene hypothesis. It surmises that when kids grow up in a really clean environment, without enough natural antigenic challenges, they may end up with allergies. This theory, if true, would explain why the number of people with allergies keeps increasing over time and why allergies are more common in more developed countries.