You are setting up for procedural sedation and would like to use propofol. What allergies should you ask of first? (Besides prior propofol allergy)
Answer: egg or soy products
Propofol is an injectable emulsion containing water, egg lecithin, soybean oil and glycerin.
Due to these ingredients, common practice is to avoid propofol in patients with pre-existing allergies to egg or soy products. 
However, data is lacking to support this practice. Two studies in the pediatric population support that propofol is probably safe in these patients.
1) One retrospective analysis of propofol being used in 76 procedures in 55 patients with egg, soy or nut allergy revealed 13 adverse events, but none due to propofol. Only one allergic reaction occurred, but this patient was later confirmed to have a first-time presentation of a latex allergy. 
2) In another study of propofol being used for 28 children with egg allergy, only one child had an [non-anaphylactic] allergic reaction. This patient had a history of anaphylactic reaction to egg and multiple food allergies. 
2) Hospira. Propofol Injectable Emulsion Safety Data Sheet. http://www.hospira.com/en/images/SDS_Propofol_Injectable_Emulsion_060214_tcm81-95540.pdf
3) Wiskin AE, Smith J, Wan SKY, Nally MWJ, Shah N. “Propofol anaesthesia is safe in children with food allergy and undergoing endoscopy.” Br J Anaesth 2015. 115(1):145-6.
4) Murphy A, Campbell DE, Baines D, Mehr S. “Allergic reactions to propofol in egg-allergic children.” Anesth Analg. 2011 Jul; 113(1):140-4.