Diseases & Conditions

Allergies


Overview, Causes, & Risk Factors

An allergy is an immune response by the body to certain stimuli in the environment that are normally harmless.

What is going on in the body?

The immune system is made up of chemical pathways and cells within the body. When these are activated, an allergic response occurs. Allergies occur in response to normally harmless triggers known as allergens. The body of a person with an allergy responds to an allergen by attacking it.

The immune response activates certain immune cells called mast cells. Mast cells trigger the release of chemicals. These chemicals include histamine and leukotrienes. They act on tissues in the body and create the allergic response.

What are the causes and risks of the condition?

No one knows for sure why some people have allergies and others do not. Family history appears to play a part in a person's development of allergies.

Some common types of allergies include the following:

  • allergic reactions to medications
  • food allergies
  • nasal allergies

  • Symptoms & Signs

    What are the signs and symptoms of the condition?

    Allergies can affect nearly any part of the body. The nose, sinuses, eyes, lungs, and skin are most affected. Symptoms may include:

  • congestion of the sinuses and nose
  • coughing
  • itching of the eyes
  • red, itching rash
  • runny nose
  • wheezing, which is a high-pitched sound heard when the person breathes

  • Diagnosis & Tests

    How is the condition diagnosed?

    Allergies are generally diagnosed with a medical history and physical examination. Blood tests and skin testing can be done to identify specific allergens.


    Prevention & Expectations

    What can be done to prevent the condition?

    There is little that can be done to prevent allergies from developing. Once they have developed, flare-ups can be reduced by allergy shots. These shots decrease a person's sensitivity to the allergen.

    What are the long-term effects of the condition?

    Most allergic reactions simply cause extreme discomfort. They usually do not pose any long-term risk to the body.

    What are the risks to others?

    Allergies are not contagious and pose no risk to others.


    Treatment & Monitoring

    What are the treatments for the condition?

    Medications used to treat allergies include the following:

  • antihistamines, which help prevent the allergic response. Many antihistamines, such as diphenhydramine, are available over the counter. Terfenadine, astemazole, loratadine, ceterizine, and fexofenadine are available by prescription.
  • anti-inflammatory medications, which reduce inflammation in the airways. These include cromolyn, nedocromil, prednisone, beclomethasone, and hydrocortisone.
  • bronchodilators, such as albuterol, to open airways and reduce wheezing
  • decongestants, such as guaifenesin, to reduce nasal congestion
  • Avoidance therapy involves removing or reducing exposure to allergens. For example, problematic foods can be identified and avoided. Air cleaners and hypoallergenic covers on mattresses can reduce nasal allergies.

    What are the side effects of the treatments?

    Antihistamines may cause drowsiness. Decongestants and bronchodilators can cause wakefulness.

    What happens after treatment for the condition?

    Treatment of allergies is generally lifelong.

    How is the condition monitored?

    Any new or worsening symptoms should be reported to the healthcare provider.


    Attribution

    Author:Mark Loury, MD
    Date Written:
    Editor:Crist, Gayle P., MS, BA
    Edit Date:09/30/01
    Reviewer:Nicholas J. Rowley, MD
    Date Reviewed:08/21/01