A list of foods to avoid if you have a soy allergy, from cofargroup.org: https://web.emmes.com/study/cofar/SOY%20Avoidance.pdf
An article regarding the safety of ingesting soy oil or soy lecithin for persons with a soy allergy:
http://www.aaaai.org/ask-the-expert/safety-of-ingestion-soy-oil-and-soy-lecithin.aspx