Normally your immune system's lymphocytes (white blood cells) travel to all parts of the body scanning the outside of proteins for chemical signatures. If it finds an invading protein, then the white blood cell returns to a lymph node where it becomes a plasma cell and generates antibodies to destroy that specific protein.
An allergy sufferer has a genetic defect that causes the white blood cells to misidentify protein and overreact to a foreign substance. If a person with a seafood allergy eats seafood, the white blood cells mistakenly think that the body is being invaded and produces many times more antibodies than are needed to fight the invaders.
Since there is not a real threat (and therefore nothing to attach to), over the next 7 to 10 days, the antibodies attach themselves to mast cells that store histamine. This is known as sensitizing to an allergen.
The next time your body is exposed to that allergen, a cascading allergic reaction occurs. During a cascading reaction all the antibodies are triggered and destroy all the mast cells they are attached to, thus releasing an abnormally large about of histamine causing runny nose, itchy skin and other symptoms.
What Happens During An Allergic Reaction?
The reaction is caused by excess amounts of histamine being released rapidly. Here are typical effects:
Histamine tries to protect the body by isolating the area with the allergen. Blood vessels shrink to reduce blood flow. This can cause drowsiness, unclear thinking and even organ failure.
As the cells and blood vessels shrink, the gaps they leave fill with fluid causing puffiness and soreness. This swelling can become severe enough to prevent sight, hearing, and breathing and make movement uncomfortable or impossible.
Skin contact with an allergen usually causes hives, itchiness and localized swelling.
Airborne allergen contact often makes breathing difficult as the throat and lungs contract. The lack of oxygen may cause drowsiness, make walking impossible, and can result in death.
The introduction of an allergen by way of blood often is the most severe. This can happen by a sting or food being digested. Blood can circulate throughout the body within 6 minutes, allowing the allergen to come in contact with all organs.
What Can You Do To Avoid A Reaction?
There are three things to help prevent an allergic reaction:
1. Avoidance. The first and most important step is avoidance of the allergen. The more exposure you have, the more likely you are to be sensitized and then have a more severe reaction. While it may be easy to avoid seafood, it is not for things like pollen. The following environmental things may help.
a. Air filtering. A good air filter will reduce the amount of airborne allergens.
b. If it is an airborne problem, wear a surgical mask while it is at its peak. The mask will filter out the majority of the pollen that would have been breathed in, thus reducing the effects of the allergen.
c. Remove carpets, keep furniture slightly away from walls and increase airflow. Carpets catch all sorts of allergens that can get stirred up each time you walk around. Moving furniture away from the walls allows air to move through the home. If air does not move freely, pockets of pollutants can build up in unused areas.
d. Make sure your vacuum and furnace have good filters. Vacuums pull up a lot of pollutants from the carpet, so be sure that they are all captured. The furnace is the primary defense against airborne allergens, since it is responsible for circulating air throughout the home.
2. Medication can greatly reduce the risk of allergic reaction as well as containing them. Antihistamines, decongestants, cromolyn sodium, corticosteroids and epinephrine are examples of things that may help. Many people find taking an antihistamine once a day during pollen season is enough to relieve their symptoms, if avoidance does not work.
3. Immunotherapy is the clinical introduction of the allergen on a regular basis and in increasing larger doses. Immunotherapy is the closet thing there is to a cure for allergies. It must be done regularly, is possibly risky and expensive, but it might work.