Allergy

Description

An allergy occurs when the body's immune system overreacts to an ordinary substance that would cause no reaction in most people. Some individuals are overly sensitive to certain substances (e.g. pollen, dust, and some foods) and the immune system responds to exposure to these materials by defending itself as if they were a threat.

The substances that produce an allergic reaction are called allergens. Allergens can enter the body by inhalation through the nose and mouth as well as orally by the ingestion of food. An allergic response to an airborne allergen is called allergic rhinitis, while an allergic response to certain foods is referred to as a food allergy.

Allergies are more common in children, though a person can develop an allergy at any age. Some allergies can go away and return later in life.

Causes

Allergies are believed to be an inherited characteristic though not everyone will develop an allergy, even if they received the genes from their parents. Development may depend on exposure to the allergen, and people may also be more susceptible to developing an allergy when their bodies are weak, after illness, or pregnancy.

Respiratory allergies can be due to air borne seasonal allergens (pollen and mold), or permanent airborne allergens (dust, pets, and cockroaches). Many types of food can cause food allergy. The most common are peanuts, tree nuts, shellfish, fish, milk, and eggs.

Treatment

The best treatment approach for allergies depends on the duration of symptoms, severity of the allergies, and the patient’s response to different treatment options. The most basic approach is to avoid the substances that cause allergic reactions. In the case of nasal allergies, many of these substances occur naturally in homes and outdoors, making medication the most common and effective option.

There are four main types of medication used to treat allergic rhinitis:

• Nasal decongestant -
  Pseudoephedrine (Afrinol*, Sudafed*) reduces congestion temporarily by making the blood vessels of the nose smaller.
• Antihistamines -
  Cetirizine (Zyrtec*) and loratadine (Claritin*, Alavert*) help with itchiness, runny nose, sneezing, and eye problems.
• Steroid nasal sprays -
  Fluticasone spray (Flonase*) and flunisolide spray relieve sinus inflammation and congestion.
• Leukotriene receptor antagonists -
  Montelukast (Singulair*) and zafirlukast (Accolate*) used to prevent the narrowing of the air passageways in the lungs.

In the case of food allergies, medications (like antihistamines and steroids) may help with symptoms, but a typical treatment strategy is to eliminate the problem foods from the patient’s diet. A potentially fatal reaction to an allergy-causing food, called anaphylactic shock, may be treated with adrenaline injections.