The Onset of Allergies

eah_image01Now that allergy season is in full swing many people find themselves reaching for their allergy meds (and a tissue). For many sufferers, allergy season represents an annual struggle between the beautiful world outside and their eyes, noses, and sinuses, which often seem to be protesting the coming of spring. These allergic responses are commonly due to an immune system response to pollen, which the body sees as a harmful, foreign substance. For more information on the biochemistry of an allergic reaction see our articles on Spring Allergies and the Antibody-Antigen Connection and the structure of an antibody.

Doctors and scientists are still not sure what causes allergic responses to otherwise harmless antigens. We do know that the prevalence of allergies has increased in recent years, and children now have a 1 in 5 chance of developing an allergy at some point in their lives. Allergies also tend to run in families; when both parents have allergies there is a 70% chance for their kids to also develop allergies. Interestingly, while there is an increased chance to develop an allergy the type of allergy does not have to match that of the parents. Even if both parents are allergic to birch trees the child might develop an entirely different seasonal allergy.

NEWS_4.17.15_Onset_Allergies_ThumbMany people find that their allergies develop while they are children, however it’s possible for someone to develop unique allergies later in life – even if they have never had an allergic reaction as a child. For example, people occasionally experience new allergies after moving to a new city, often due to the presence of plants and grasses that they did not experience in their previous home. Recently, the case of a young boy highlighted an even more surprising way to develop allergies – through a common blood transfusion!

A report in the Canadian Medical Association Journal tells the story of a young boy who developed food allergies after receiving a blood plasma transfusion. The boy, an 8 year old with no history of food allergies, had a strong allergic reaction after eating salmon and then a second time after eating peanuts, two foods that he had commonly eaten in the past. The doctors investigated these reactions and discovered that the plasma donor was also allergic to these foods and had passed the antibodies to the boy during the transfusion. Fortunately, the antibodies can only persist in the blood for a short time, and within 6 months the young patient was no longer allergic to either food.

So why don’t doctors screen for allergies when accepting donated blood? It turns out that detecting antibody levels in the blood is not always a good predictor of allergies, and setting a lower antibody cutoff could eliminate otherwise healthy blood. Fortunately, these sorts of reactions are extremely rare and are unlikely to be life threatening. 

NEWS_4.17.15_Red_Cross_FlagIf you are interested in exploring these topics further in your classroom we offer exciting, hands-on experiments examining blood typing ( and antibody-antigen reactivity ( Finally, remember that donated blood is always in demand – to find out more information, including donor requirements and locations, please check out the American Red Cross website here (


%d bloggers like this: