The Doctor Is In

By DAMON RASKIN, M.D. | Special to the Palisadian-Post

Q:My aunt was diagnosed with an allergy to cashews in her 50s. Prior to that, she had no signs of being allergic to them, which got me thinking about it: What causes allergies to develop later in life versus ones that are discovered much younger (like when someone is a baby)? Is it possible to develop an allergy at any age to anything, like dairy, eggs or nuts?

I distinctly recall being in my second year of medical school and receiving a phone call from my mom telling me that while my parents were on vacation in Hawaii, my dad was rushed to the hospital with a severe allergic reaction to the shrimp he had at dinner.

He turned red, developed hives and then began to get a swollen lip. He got to the hospital in time for treatment, and he was fine after receiving the appropriate medications.

The strange thing was that he had eaten shrimp his entire life without a problem. He has not eaten any since.

Allergies, which are abnormal immune responses to typically harmless substances, can develop at any age, from early childhood to later stages of life. Understanding the factors that lead to early-onset versus adult-onset allergies provides insight into the complex interplay between genetics, environment and the immune system.

While some individuals are born with a predisposition to allergies that emerge in infancy or childhood, others may develop allergies much later in life, even to substances they have previously encountered without issue. So, what causes this difference in timing, and is it possible to develop an allergy to anything at any age?

Allergies that develop early in life are often the result of genetics. Children born to parents with allergies have a higher likelihood of developing similar conditions, a phenomenon known as atopy. This genetic susceptibility primes the immune system to overreact to common allergens like pollen, pet dander, certain foods or dust mites.

I come from a long line of family members who are allergic to cats. I found out about my allergy when going to a friend’s house in the first grade who had a cat, and I had to leave after 15 minutes because I could not stop sneezing.

Infants and young children are especially vulnerable to food allergens. Common culprits include milk, eggs, tree nuts and shellfish. Immature immune systems are more sensitive to new substances, and once they encounter a particular allergen, they may produce an exaggerated immune response.

Environmental factors may also play a significant role. For instance, children exposed to high levels of pollution, tobacco smoke or even cleaning chemicals have been found to have higher rates of asthma or other allergic reactions. Early microbial exposure, such as interactions with pets, can also influence immune development, and either promote or even prevent allergies, depending on the exposure.

Allergies later in life, like with my dad, are more mysterious. One theory is that the immune system changes over time, particularly as we age or encounter new environmental stressors. In some cases, immune systems weaken due to age, illness or chronic conditions that may cause an allergic reaction to emerge as the body’s defense mechanisms shift.

On the other hand, heightened immune activation caused by stress, infections or hormonal changes, such as in pregnancy or menopause, can prompt the immune system to overreact to substances it previously tolerated.

In addition, relocating to a different part of the country can expose adults to new allergens. Changes in diet or a new climate may introduce new plants or molds that can trigger an allergic response for the first time in adulthood.

So yes, it is possible to develop an allergy at any age, underscoring the need for ongoing awareness and proper management of allergic reactions throughout life. Listen to your body, and if you develop any new allergy symptoms, please speak to your medical provider.