Allergies

Allergies

Definition  :

Allergies occur when your immune system reacts to a foreign substance such as pollen, bee venom or pet dander.

Your immune system produces substances known as antibodies. Some of these antibodies protect you from unwanted invaders that could make you sick or cause an infection. When you have allergies, your immune system makes antibodies that identify your particular allergen as something harmful, even though it isn't. When you come into contact with the allergen, your immune system's reaction inflames your skin, sinuses, airways or digestive system.

The severity of allergies varies from person to person and can range from minor irritation to anaphylaxis — a potentially life-threatening emergency. While allergies can't be cured, a number of treatments can help relieve your allergy symptoms.

Symptoms:

Allergy symptoms depend on your particular allergy, and can involve the airways, sinuses and nasal passages, skin, and digestive system. Allergic reactions can range from mild to severe. In some severe cases, allergies can trigger a life-threatening reaction in your body known as anaphylaxis.
Hay fever, also called allergic rhinitis, may cause:

• Congestion
• Itchy, runny nose
• Itchy, watery or swollen eyes (conjunctivitis)

Atopic dermatitis, an allergic skin condition also called eczema, may cause:

• Itchy skin
• Red skin
• Flaking or peeling skin

A food allergy may cause:

• Tingling mouth
• Swelling of the lips, tongue, face or throat
• Hives
• Anaphylaxis

An insect sting allergy may cause:

• A large area of swelling (edema) at the sting site
• Itching or hives all over your body
• Cough, chest tightness, wheezing or shortness of breath
• Anaphylaxis

A drug allergy may cause:

• Hives
• Itchy skin
• Rash
• Facial swelling
• Wheezing
• Anaphylaxis

Anaphylaxis
Some types of allergies, including allergies to foods and insect stings, have the potential to trigger a severe reaction known as anaphylaxis. A life-threatening medical emergency, this reaction can cause you to go into shock. Signs and symptoms of anaphylaxis include:

• Loss of consciousness
• Lightheadedness
• Severe shortness of breath
• A rapid, weak pulse
• Skin rash
• Nausea and vomiting
• Swelling airways, which can block breathing

When to see a doctor
You may want to see a doctor if you have symptoms you think may be caused by an allergy, especially if you notice something in your environment that seems to trigger your allergies. If you have symptoms after starting a new medication, call the doctor who prescribed it right away.

For a severe allergic reaction (anaphylaxis), call 911 or your local emergency number or seek emergency medical help. If you carry an epinephrine auto-injector (such as EpiPen, EpiPen Jr or Twinject), give yourself a shot right away. Even if symptoms improve after an emergency epinephrine injection, a visit to the emergency department is still necessary to make sure symptoms don't return when the effects of the injection wear off.

If you've had a severe allergy attack or any signs and symptoms of anaphylaxis in the past, make an appointment to see your doctor. Evaluation, diagnosis and long-term management of anaphylaxis are complicated, so you'll probably need to see a doctor who specializes in allergies and immunology.

Causes :
 
An allergy starts when the immune system mistakes a normally harmless substance for a dangerous invader. The immune system then produces antibodies that are always on the alert for your particular allergen. When you're exposed to the allergen again in the future, these antibodies release a number of immune system chemicals, such as histamine, that cause allergy symptoms.
Common allergy triggers include:

• Airborne allergens, such as pollen, animal dander, dust mites and mold
• Certain foods, particularly peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk
• Insect stings, such as bee stings or wasp stings
• Medications, particularly penicillin or penicillin-based antibiotics
• Latex or other substances you touch, which can cause allergic skin reactions

Complications :

Having an allergy increases your risk of certain other medical problems, including:

• Anaphylaxis. If you have severe allergies, you're at increased risk of this serious allergy-induced reaction. Anaphylaxis is most commonly associated with food allergy, penicillin allergy and allergy to insect venom.
  
• Another allergy. Having one type of allergy also increases your risk of becoming allergic to something else.
  
• Asthma. If you have an allergy, you're more likely to have asthma — an immune system reaction that affects the airways and breathing. In many cases, asthma is triggered by exposure to an allergen in the environment (allergy-induced asthma).
  
• Atopic dermatitis (eczema), sinusitis, and infections of the ears or lungs. Your risk of getting these conditions is higher if you have hay fever, a pet allergy or a mold allergy.
  
• Fungal complications of your sinuses or your lungs. You're at increased risk of getting these conditions, known as allergic fungal sinusitis and allergic bronchopulmonary aspergillosis, if you're allergic to mold.

Treatments and drugs:

Allergy treatments include:

• Allergen avoidance. Your doctor will help you take steps to identify and avoid your allergy triggers. This is generally the most important step in preventing allergic reactions and reducing symptoms.
  
• Medications to reduce symptoms. Allergy medications can help reduce your immune system reaction and ease symptoms. The drugs you use depend on the type of allergy you have. They can include over-the-counter or prescription medications in the form of oral medications, nasal sprays or eyedrops. Some common allergy medications include corticosteroids, antihistamines, decongestants, cromolyn sodium and leukotriene modifiers.
  
• Immunotherapy. For severe allergies or allergies not relieved by other treatment, your doctor may recommend allergy shots (immunotherapy). This treatment involves a series of injections of purified allergen extracts, usually given over a period of a few years.
  
• Emergency epinephrine. If you have a severe allergy, your doctor may give you an emergency epinephrine shot to carry with you at all times. Given for severe allergic reactions, an epinephrine shot (EpiPen, EpiPen Jr, Twinject) can reduce symptoms until you get emergency treatment.