When we talk about allergies, we are usually discussing seasonal allergies, with nothing more distressing than a sneezing fit or a runny nose as a result of pollen in the air.
But food allergies are much different – they are quieter, with little warning that trouble awaits.
Research suggests that food allergies start with a protein that passes through the intestine largely undigested. This is quite unusual because the stomach is full of acid and enzymes, and the intestinal churning reduces food to tiny fragments of its simplest component parts (fats, carbs and proteins). But this rare, relatively intact protein attracts the attention of the immune system. The system mistakenly considers it an invader, and produces an antibody called Immunoglobulin E to fight it. The antibodies circulate quietly, ever vigilant.
This is a set up for the worst type of food allergy: an antibody-caused reaction. In a person allergic to peanuts, for example, the simple introduction of a bit of peanut protein into otherwise harmless food can cause a severe allergic reaction within minutes. This occurs so quickly because the antibodies are already there. They attach to the “invading protein,” triggering a massive release of histamine, which causes blood vessels to dilate and leak.
The histamine reaction that happens from seasonal allergies is obvious. Swollen and leaky vessels plug your nose, and produce a runny nose, scratchy throat and perhaps some wheezing.
But with food allergies, this histamine reaction happens deep within the body. In a worst-case scenario when someone is severely allergic to a food, this can cause widespread dilation of blood vessels, dropping the blood pressure to critical levels. The lungs become congested, and can cause a full-fledged emergency with anaphylactic shock.
At this point, a person must use an EpiPen, which they prudently always carry if they know of their allergy. A self-injected dose of adrenaline contracts the vessels and brings the blood pressure back up, and clears the lungs. This emergency still requires paramedics, but the person has improved his or her chances of a full recovery immensely.
Thankfully, most allergic reactions to food aren’t quite so severe. Hives would be my first choice if I could pick my allergic reaction. Hives are large, red blotches that form on the skin and often spread or fade before your eyes. These are easily banished with an oral dose of Benadryl.
People can also have intestinal symptoms that are sort of like hives on the inside. Common symptoms are cramps and abdominal pain, vomiting or diarrhea, easily confused with gastroenteritis. But if due to a food allergy, antihistamine will be effective in bringing relief.
Peanut allergies are one of the worst food allergies, and recently some progress has been made in preventing them. New research is finding that some exposure to peanut protein from a very young age seems to condition the immune system to not overreact.
Food allergies of the milder variety are pretty common, but they can be puzzling for patient and healthcare provider alike.
As we are finding out more often, early childhood counts in making immunological peace with the rest of the world.
Donald Bucklin, MD (Dr. B) is a Regional Medical Director for U.S. HealthWorks and has been practicing clinical occupational medicine for more than 25 years. Dr. B. works in our Scottsdale, Arizona clinic.
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