How Things Work: Allergies
Sneezing, coughing, and itchy eyes bring torment to many during what should be the joyous coming of spring. Allergies, seemingly trivial compared to other ailments, are one of the biggest public concerns due to the sheer number of people that suffer from them.
The specific form of allergies that brings sneezing, coughing, and itchy eyes is called allergic rhinitis — meaning that it causes inflammation of the mucus membranes in the nose. More serious allergies can be life threatening, such as severe food allergies to peanuts and crustaceans. Other allergies can develop over time in reaction to certain cosmetics and food additives.
Allergies are an immune system response to antigens, or pathogenic particles. The immune system responds to antigens by producing antibodies, the defensive proteins that allow the immune system to find invading substances. The antigens in food are harmless; otherwise many people would suffer from food toxicity. According to the Utrecht Center for Food Allergy, when an allergy-causing antigen is present in the body, immunoglobulin E, or IgEs, antibodies that fight antigens, are produced and released.
If an antibody comes in contact with its antigen, the antibody causes the release of factors that result in common allergy symptoms. These factors trigger the body to begin three basic processes: blood vessels expand to increase their permeability which causes inflammation; stimulation of mucus secretion, which is seen as a runny nose; and stimulation of nerves, which induces sneezing. The first process increases blood flow to the area and allows immune cells through the blood vascular walls so they can begin to fight the expected infection. The latter two processes block incoming particles from reaching the cells and attempt to physically remove the invading species.
One common way of detecting which substances people are allergic to is a radioallergosorbent test (RAST), which looks for the presence of IgEs against known antigens by injecting the antigens into the body. Another technique is a skin prick test, which exposes patients to a variety of antigens; the doctor examines the prick site to analyze redness and swelling in the area. However, these tests have low accuracy. Just because IgEs are present in a patient doesn’t mean that patients will develop a clinical response upon exposure; redness and swelling are highly subjective and are difficult to measure.
According to the Utrecht Center, a double blind placebo-controlled food challenge is the best test despite its high cost. The test involves having patients consume foods that may or may not contain various antigens in various concentrations; both of these variables are initially unknown to both the doctor and the patient. These tests, however, are not often administered because they take several days to complete and require specially trained personnel to administer.
The worst possible outcome of any allergic reaction is anaphylaxis, or allergic shock, which is caused by extreme immune responses. Blocked or spasmodic air ways cause breathing difficulties. Dangerously low blood pressure then leads to unconsciousness and possibly heart failure. Less severe symptoms are hives or swelling, dizziness, and nausea.
Allergies present a huge market for pharmaceutical companies. Unlike antibiotics for infections, patients never stop taking allergy treatments, which allows for continuous revenue. In addition, according to the Asthma and Allergy Foundation of America, allergies in the United States appear to be increasing. During every exposure to foreign particles, the body will make antibodies, making it increasingly important to examine the nature of products we use and are exposed to.