Thank you for your inquiry.
The admonition against allergic individuals as blood donors is based upon the rare reaction due to the transmission of IgE against specific allergen to a person who is not allergic to that allergen. The IgE transferred by this process can bind to the recipient's masts cells and remain there for several weeks. Upon exposure to the allergen in question, the recipient could have an allergic reaction. The first report of such an event was an article written by Ramirez (1), and there have been rare reports subsequent to this initial event (2).
However, these events are exceedingly rare, and there is controversy as to screening for allergy or preventing allergic individuals from donating blood (see abstract by Wilhelm and another by Stern, et al., copied below). In fact, there is no universally accepted admonition against allergic individuals donating blood (see here). I have seen some centers recommend that allergic patients not donate blood if they are having acute allergic symptoms, but allow them to do so when they are asymptomatic, and other centers have no admonition whatsoever against an allergic individual donating blood regardless of whether or not symptoms are present.
So in summary, the abstracts below discuss the arguments pro and con against allergic individuals donating blood, but in general, at least in my experience, the presence of allergy will not automatically eliminate a donor. Neither antihistamines nor inhaled medications to my knowledge are a contraindication.
Thank you again for your inquiry and we hope this response is helpful to you.
Vox Sang. 1995;69(3):217-21.
Impact of allergy screening for blood donors: relationship to nonhemolytic transfusion reactions.
Wilhelm D1, Klüter H, Klouche M, Kirchner H.
1Institute of Immunology and Transfusion Medicine, School of Medicine, University of Lübeck, Germany.
There has been some discussion whether the atopic disposition of a blood donor is associated with a potentially higher incidence of hypersensitivity nonhemolytic transfusion reactions (NHTRs). Serum samples from patients who had suffered from NHTRs and samples from the platelet concentrates (PCs) responsible for the reactions were examined for total and specific IgE as diagnostic markers for allergic events. In addition, the allergy prevalence among 1,088 blood donors was determined to analyze the allergy prevalence among our blood donors. Our results indicate that in 90% of cases, allergic NHTRs were associated with specific IgE antibodies in the recipient's serum, indicating the allergic disposition of the patient. In contrast, specific IgE antibodies were detected in only 22% in the transfused PCs. However, among all investigated NHTRs, there was not a single case in which specific IgE antibodies were detected exclusively in the PC. The allergy prevalence among our blood donors was about 26%. In our opinion, the few cases in which the allergic disposition of blood donors in combination with the allergic disposition of the recipients was associated with NHTRs reflects the allergy prevalence among our blood donors in general (26%). On the basis of these findings, we conclude that allergy diagnosis for blood donors is only of minor value in the prevention and prediction of NHTRs, whereas allergy diagnosis for patients who require multiple PC transfusion might be helpful
Vox Sang. 1995;69(2):114-9.
Is allergy screening of blood donors necessary? A comparison between questionnaire answers and the presence of circulating IgE antibodies.
Stern A1, van Hage-Hamsten M, Sondell K, Johansson SG.
1Department of Clinical Immunology, Karolinska Hospital, Stockholm, Sweden.
We investigated 477 consecutive blood donors on order to find the predictive value of a questionnaire as a screening method for preventing passive transfer of IgE antibodies to common allergens that might cause transfusion reactions. Of the 477 donors, 119 (24.9%) claimed to be allergic and 358 (75.1%) recorded no allergic complaints. Serological examination with Phadiatop and a multi-allergen mix for food (fx5) detected IgE antibodies in only 54.5% of the allegedly allergic blood donors. Among the allegedly asymptomatic donors, 12.3% showed positive results in these tests. Subsequently, radioallergosorbent test analyses with common inhalant and food allergens were performed to specify the IgE responses obtained. Our results demonstrate a remarkable difference between the questionnaire answers and the serological measurements of IgE antibodies and raise the question of whether - and if so, what kind of - allergy screening is warranted among presumptive blood donors.
1) Ramirez M. Horse asthma following blood transfusion. J Am Med Assoc 1919; 73:984-985.
2) Arnold Donald M, Blajchman Morris A, DiTomasso Julie, Kulczycki Myron, and Keith Paul. Passive Transfer of Peanut Hypersensitivity by Fresh Frozen Plasma. Arch Intern Med 2007; 167(8):853-854. doi:10.1001/archinte.167.8.853.
Phil Lieberman, M.D.