The first sign that something was wrong with Shon Dwyer’s son was as sudden as it was dramatic. Dylan was 10 months old when she spotted quarter-sized hives on his face, and soon after, Dwyer learned her little boy had a peanut allergy that will continue to affect the family’s life for years to come.

“We’ve had to change how we grocery shop, how we prepare food, where we can go,” says Dwyer, director of the University of Michigan Health System’s Orders Management Project. “We always have an emergency bag because the peanut allergy is completely unpredictable.”

Like many families, the Dwyers face the daily uncertainty that goes hand in hand with such allergies. Dylan, now 7 years old, may be perfectly fine one minute, and then may experience anaphylaxis -  a severe reaction in which a loss of oxygen can cause one’s body to go into shock, and which can lead to death.

“Anaphylaxis generally comes on very quickly, generally within five minutes to 60 minutes, as opposed to other allergic symptoms such as hay fever or allergic rhinitis,” says Marc S. McMorris, M.D., director of the U-M Health System’s Food Allergy Service.

“The problem is that you don’t know if that’s going to happen with the next exposure to the food or five exposures from now. So you have to be very careful with regard to avoidance and taking appropriate measures to avoid those allergens that you have sensitivity to,” says McMorris, clinical associate professor in the Department of Internal Medicine’s Division of Allergy and Clinical Immunology, and in the Department of Pediatrics and Communicable Diseases at the U-M Medical School.

That’s why Dwyer always carries an epinephrine (adrenaline) self-injector, or EpiPen, which is commonly used to control anaphylaxis among people with allergies to foods, bee stings, latex and medications such as penicillin.

The good news, McMorris notes, is that life-threatening allergies such as Dylan Dwyer’s are not terribly common.

“About 20 to 30 percent of our population is allergic to something, whether it’s trees or grass or weeds or foods, or some other allergen,” McMorris says. “Within the context of that, a very small percentage is actually prone to having life-threatening allergic reactions or anaphylactic reactions.”

McMorris recommends that people with potentially life-threatening allergies should be evaluated by their primary care doctors, and subsequently referred to an allergist, to determine if they need aggressive therapies such as an epinephrine injector. Families with a history of allergies would be wise to avoid high-risk foods during early childhood, he says.

He also notes that while serious food allergies tend to occur initially during early childhood, adults can develop allergies to foods such as nuts or seafood, or to bee stings.

Common symptoms of food allergies:

•   Rash
•   Hives
•   Swelling
•   Nausea
•   Vomiting
•   Diarrhea
•   Swollen lips or tongue
•   Wheezing, asthma and difficulty breathing
•   Aphylactic shock (low blood pressure due to an allergic reaction), which can be fatal if untreated

Foods that commonly cause allergic reactions

•   Peanuts
•   Nuts (almonds, cashews, walnuts, pecans, hazelnuts, Brazil nuts)
•   Milk
•   Eggs
•   Soybeans
•   Fish and shellfish

Statistics from the National Institute of Allergy and Infectious Diseases

•   More than 50 million Americans suffer from allergic diseases.
•   Allergies are the sixth-leading cause of chronic disease in the United States, costing the health care system $18 billion annually.
•   Experts estimate food allergies occur in 6 to 8 percent of children 4 years or younger, and in 4 percent of adults.
•   Approximately 150 Americans, usually adolescents and young adults, die annually from food-induced allergic reactions.