Soy lecithin is derived from highly processed soy oil and has very little, if any, soy protein (100-500 ppm). Most allergists do not recommend that patients with soy allergy avoid soy lecithin. Organizational on-line sources (FARE, FAARP, CoFAR) indicate that food products containing soy lecithin can be consumed safely by nearly all patients with soy allergy. A literature search found few case reports of allergic reactions that have been attributed to soy lecithin. The degree of risk for use of soy lecithin-containing medications in patients who have soy allergy has not been extensively studied. Considering the small amount of protein present, the risk of a reaction from these medications is thought to be very small, yet there are case reports of reactions. Consequently, the use of these medications in highly sensitive soy-allergic patients is usually avoided. However, if no alternatives exist and the medication is necessary, after a discussion of risks vs benefits, one might consider administration of the first dose under medical observation.
I hope this information is helpful to you.
Jacqueline A. Pongracic, MD, FAAAAI