Oils commonly used in the UK are derived from rapeseed, sunflower seed, soya, maize, palm, coconut and palm kernel. Oils can also be derived from peanuts, sesame and tree nuts (such as walnut).
When oils go through a refining process, this removes the proteins (the components of a food that cause allergic reactions) to the point where they are barely, if at all, detectable even by very sensitive techniques. Generally speaking, it is thought that people with allergy to a specific food can eat oil derived from that food so long as the oil has been fully refined. However, research is still incomplete in this area.
One oil that has been subject to research is soya. The safety of refined soya oil for people with soya allergy was scientifically established by clinical trials both in Europe and the US and acknowledged by the European Food Safety Authority (EFSA) in 2007. So although unrefined soya oil does have to be labelled when it appears in pre-packed food, refined soya oil does not.
Research conducted in Southampton showed that refined peanut oil is safe for the vast majority of people with peanut allergy. However, EFSA said some doubt remained about whether this held true for all refined peanut oils. As a result of this judgment, refined peanut oil does have to be labelled when it appears in pre-packed food, as does unrefined peanut oil.
Reference: Hourihane JO, Bedwani SJ, Dean TP, Warner JO (1997). Randomised, double blind, crossover challenge study of allergenicity of peanut oils in subjects allergic to peanuts. BMJ 1997 Apr 12;314(7087):1084-8.
Nut oils and sesame oil
Oils such as sesame and walnut do contain some unrefined oil and will most likely present a risk.
Other vegetable oils
At the time of publication of this article (January 2012), other oils such as rapeseed, sunflower, maize, palm, coconut and palm kernel have not been subjected to research to test whether refining them makes them safe for people with allergies to those specific foods.
However, we can say that where these oils are used in pre-packed food, it is almost certain that they will have been refined. If you are allergic to sunflower seeds, for example, the risk of an allergic reaction from eating refined sunflower oil will be extremely low. Although it is not possible to be 100 per cent certain about this, it is a fact that the Anaphylaxis Campaign helpline hears of NO allergic reactions that have been proven to be triggered by refined vegetable oils.
Some people with coconut allergy wonder whether it is safe for them to eat palm oil.. There is no reason to suspect a link between coconut allergy and palm oil but these people may prefer to avoid unrefined palm oil. The refined oil is extremely unlikely to cause them problems and any palm, palm kernel or coconut oils used in processed foods will be fully refined.
A code of practice for the food industry
In order to assist in the risk management of allergens in the oils and fats sector, FEDIOL (the European oilseed federation) has developed a code of good practice laying down provisions for the production and labelling of all the above mentioned oils (unrefined and fully refined).
July 2011 research
An improved method has been developed to determine residual protein in refined oils, a potential trigger of allergic reactions. Reassuringly, the scientists who developed the method confirmed that while unrefined oils contain significant amounts of protein, full refining reduces the content by at least 100-fold.
They concluded that refined vegetable oils such as soya or peanut are highly unlikely to trigger allergic reactions. In the case of soya, for example, even the most sensitive people with soya allergy would need to eat at least 50g of highly refined oil to experience subjective symptoms, according to the research.
The study team comprised scientists based in the USA and UK, including the Institute of Food Research at Norwich. To read an abstract of their work, click here: http://www.ncbi.nlm.nih.gov/pubmed/21250696