Generally, vegetable oils are highly refined, meaning that they are processed in such a way to remove the majority of the protein present in the crude (raw) form. It is the protein in foods that act as the allergen, and is responsible for causing allergic reactions as a result of eating the food. The refining of vegetable oils decreases the amount of protein by approximately 100-fold, which significantly decreases the chance of vegetable oils causing allergic reactions. Unfortunately, crude and some refined vegetable oils do contain some vegetable proteins, which may cause allergic reactions in very sensitive people with food allergies.
Peanut OilPeanut allergy has become increasingly common over the past few years, and now affects 1-2% of populations living in Westernized countries. Avoidance of peanut is quite difficult, and is it often a hidden ingredient in many prepared foods. Peanut oil is commonly used in cooking and food processing, and is available in both crude (often referred to as "gourmet", "cold pressed" or "raw") and refined (also referred to as “heat processed”). The refining process of peanut oil virtually eliminates the presence of peanut protein; although even crude peanut oil contains a very small amount -- micrograms per milliliter – of peanut protein. Most people with peanut allergy don’t experience allergic reactions until they’ve eaten 50 to 100 milligrams of peanut protein – meaning that a person with peanut allergy would likely have to consume liters of crude peanut oil to cause an allergic reaction. In fact, a study published in 1997 found that less than 10% of peanut allergic patients experienced allergic reactions (all of which were quite mild) after consuming various amounts of crude peanut oil. None of the 62 patients studied reacted to refined peanut oil.
Another study published in 2008 sought to determine if allergic antibodies to peanut in blood samples from people with peanut allergy would react to peanut protein found in peanut oil in a test called an immunoblot. Reactions did occur, but only in blood samples with extremely high levels of allergic antibody to peanut. It is important to realize that this study looked at a blood test, rather than a test to see if a person with peanut allergy would experience an allergic reaction after eating peanut oil.
Soybean OilLess information is available regarding soybean oil and allergic reactions, although there are a number of cases of allergic reactions reported in the medical literature to foods, as well as medications, that contained soybean oil. It is likely that, similar to peanut, crude soybean oil contains more protein than refined soybean oil. While soy is considered to be a common food allergy, it is more of an issue in young children, and adults frequently outgrow peanut allergy. In fact, during my 10 years of practicing allergy/immunology, I believe I can only recall seeing one or two adults with significant soy allergy. This is likely the reason why we don’t see more reports of food allergy to soybean oils.
Sunflower Seed OilSunflower seed allergy is not particularly common, although I have seen a handful of patients in my practice recently with this type of food allergy. There are a few reports in the medical literature of people experiencing allergic reactions to sunflower seed oil, although a study published in 1986 found no reaction to crude or refined sunflower seed oil in 2 patients with known anaphylaxis after eating sunflower seeds.
Sesame Seed OilSesame is becoming a more common food allergy in recent years, and like peanut allergy, severe allergic reactions are quite common as a result of sesame allergy. Sesame seed oil is different than many of the other vegetable oils in that it is used as a flavoring for foods. For this reason, sesame seed oil is typically crude, and therefore contains significant sesame proteins. Allergic reactions to sesame seed oil have been reported in the medical literature, and therefore a person with a sesame seed allergy should strictly avoid sesame seed oil.
Other Vegetable OilsThere are a number of other vegetable oils used in cooking and prepared foods. These include corn oil, safflower oil, canola oil, palm oil, palm kernel oil, and coconut oil. With the exception of a single report of coconut oil allergy contained in a baby formula published in 1994, there are no reports of food allergy to these vegetable oils published in the medical literature. It is likely that these oils are refined and therefore contain little, if any, protein that could trigger an allergic reaction.
Therefore, if a person is allergic to a particular food from which a vegetable oil is obtained (such as peanut, soybean or sunflower), the crude oil should be avoided. Given that the refined oil contains little or no protein, it should be safe for this type of oil to be consumed. In the case of sesame seed oil, or any other vegetable oil that is used to flavor a food, a person with sesame seed allergy should avoid consuming sesame seed oil.
Read more about allergy to food additives and preservatives.
Ramazzotti M, et al. Analytic Investigations on Protein Content in Refined Seed Oils: Implications in Food Allergy. Food and Chemical Toxicology. 2008;46:3383-8.
Crevel RWR, et al. Allergencity of Refined Vegetable Oils. Food and Chemical Toxicology. 2000;38:385-93.
Hourihane JOB, et al. Randomised, Double Blind, Crossover Challenge Study of Allergenicity of Peanut Oils in Subjects Allergic to Peanuts. BMJ. 1997;314:1084.
Kanny G, et al. Sesame Seed and Sesame Seed Oil Contain Masked Allergens of Growing Importance. Allergy. 1996;51:952-7.
Halsey AB, et al. Sunflower Oil is not Allergenic to Sunflower Seed-Sensitive Patients. J Allergy Clin Immunol.1986 Sep;78(3 Pt 1):408-10.
DISCLAIMER: The information contained in this site is for educational purposes only, and should not be used as a substitute for personal care by a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition.