Grown-ups Get Food Allergies Too!

Two and a half million Canadians have at least one food allergy, and the numbers are rising.  It's commonly believed that most food allergies begin in childhood. Now, a new study has a surprising conclusion. 

Researchers at Science and Outcomes of Allergy or Asthma Research (SOAAR) at Northwestern University in Chicago conducted a national survey of U.S. households to check on the prevalence of food allergies among children.  They also surveyed 40,000 adults in the U.S. in which they looked at the prevalence and severity of food allergies -- and asked at what age the allergy began.  What they found was unexpected.  Forty-five per cent of adults with food allergies developed them as adults -- not as children.  

The most common food allergy among adults surveyed is shellfish.  According to the survey, 3.6 per cent of U.S. adults are allergic to shellfish.  That is up 44 per cent from the 2.5 per cent prevalence reported in a study back in 2004. The survey also found that 1.8 per cent of adults are allergic to tree nuts, up 260 per cent from the 0.5 per cent reported in 2008.  There were also some important findings based on ethnic origin.  People of Asian descent were 2.1 times more likely to have a shellfish allergy, and those of Hispanic origin were 2.3 times more likely to have a peanut allergy.

The results are surprising to almost everyone with a stake in this.  There is a widely-held belief that the vast majority of food allergies begin in childhood.  That's what I was taught.  That belief is so entrenched that doctors are skeptical when adult patients say they think they've developed a food allergy.  Doctors have been known to chalk up the symptoms of a shellfish allergy to acid reflux. 

Because I work in the ER, I see the worst cases of anaphylaxis, and I definitely see adults with newly-diagnosed food allergies. Until recently, there have been few studies of adults.  A 2014 study by the same group of Northwestern University researchers found that the older a patient is when diagnosed with food allergies, the more likely they are to have a severe reaction.

Why do researchers think more adults have food allergies? The assumption that most food allergies begin in childhood has meant that researchers have ignored adults.  With children, the thinking that they failed to develop a tolerance to the foods that they encounter early in life.  With adults, it's a case of losing tolerance to foods that they've already been able to eat -- in some cases, for decades. The trigger for that may be something in the environment, like a virus or some other sort of infection, or a change in where they live.

Part of the problem is lack of recognition. Patients themselves may not recognize they have a food allergy. Until they get an anaphylactic reaction, they're likely to chalk up allergy symptoms to a minor food intolerance.

The take home message is that grown-ups are almost as prone to food allergies as children.  And it may be an allergy to something they've loved eating since childhood. The most likely culprits are shellfish and tree nuts.  Don't ignore the symptoms however vague or improbable they seem.  Early symptoms include a sick feeling in the pit of your stomach coupled with anxiety and a sense that you no longer like a food that used to be your favorite.

If you have symptoms of anaphylaxis include a burning feeling in the mouth, swelling and itching around the face, throat tightening, nausea, wheezing or shortness of breath, call 911 and get to the hospital.  Ask your doctor to refer you to an allergist, and be prepared to face some skepticism about it.  Like kids, adults need to avoid foods to which they're allergic, and carry an Epi-Pen. 

The unfortunate reality is that age is no barrier to being diagnosed with a food allergy.