Can soybean oil and soy lecithin trigger an allergic reaction?


I’m drafting this post late one night in the hot muggy dark when I should be sleeping, would rather be sleeping, because I’ve spent the past hour awake and unable to successfully switch off. I think it’s because my brain is still percolating on today’s research and trying to fit it in with all of the other health-related research of the last few months; it’s rather like trying to put together one of those large jigsaw puzzles where you only have a vague idea of the expected outcome because you’ve lost the lid to the box which has the finished picture.

If you, or a family member or loved one, has been diagnosed with a soy allergy then you’re probably familiar with the phrasing that “the vast majority” (emphasis on the air quotes) of sufferers will not experience an allergenic reaction to soybean oil or soy lecithin. This does then rather prompt the question of, ‘Why not?’

What is Soybean Oil?

This oil is incredibly widely used worldwide. In the USA particularly it is apparently the most widely used edible oil taking up 55% of the market share in 2014. It’s cheap to obtain (because it’s grown year round in many countries as livestock feed), doesn’t have a lot of inherent flavour, and is proven to be highly adaptable and stable for uses within the food industry.

This is problematic if you’re allergic to it because it can appear in anything from dried fruit (like sultanas), to peanut butter, to cookies, to non-dairy coffee creamers. Anything that contains undeclared “vegetable oils” becomes suspect because there is a high likelihood that part (or all) of that is soybean oil.

The soybeans are cracked, heated, rolled, solvent-extracted with hexanes, refined, and then may be further blended and/or hydrogenated (partially or fully). Some sites discuss health concerns about soybean oil purely to do with potential adverse health concerns relating to hexanes, hydrogenation, or trans-fats. I haven’t researched those sufficiently to have formed an opinion so I’ll leave that to readers to follow up on should they wish.

What is soy lecithin?

To make soy lecithin, soybean oil is extracted from the raw soybeans using a chemical solvent (usually hexane). Then, the crude soy oil goes through a ‘degumming’ process, wherein water is mixed thoroughly with the soy oil until the lecithin becomes hydrated and separates from the oil. Then, the lecithin is dried and occasionally bleached using hydrogen peroxide. (1) (2).

Soy lecithin is used as an emulsifier to help stabilize food products and prevent them from separating out into their component forms (like in chocolate or margarine). Sometimes it will be declared on food packaging in full (i.e. soy lecithin), other times there is simply an additive number; 322 is almost always soy, 471 often so.

Can soybean oil or soy lecithin trigger an allergic reaction?

That’s really the crux of the matter if you (or loved one) has been diagnosed as allergic to soy. I’ve seen the full gamut of opinion online and in published books.

Some sources will argue that the high heats used to produce soybean oil and soy lecithin denature the allergenic proteins; others argue that there are no soy proteins in these products (or so few that they can’t cause a reaction). Admittedly, some of these articles I suspect of having a commercial bias.

Some take the middle ground and say that “the vast majority” of people sensitive to soy will not have an allergic reaction and to discuss it with your medical specialist (which you should do).

Some argue that it is difficult to accurately test concentration levels of soybean protein in these products and that often there is no legal requirement to do so (or insufficient oversight for sufficient regulatory surety). For instance, one study in 2001 found that the level of proteins found in six lecithin samples ranged from 100 to 1,400 ppm (parts per million); that’s a big range even in such a small sample size. By comparison, the 2013 ruling by the FDA required that gluten-free foods contain less than 20 ppm (3).

There don’t seem to be large-scale studies into using these products to trigger IgE antibodies. Small studies publishing in 1998 seem to suggest that these can cause an allergic reaction but only in some people that are allergic to soy (4, 5). One (non-medical) article suggested that sensitivity to soy lecithin may be linked to gut permeability (i.e. the more damaged and inflamed the gut has become, the more susceptible one becomes to even the tiniest trace of soy protein).


Yes, it is possible to have an allergic response to soybean oil and/or soy lecithin. Miss 2 appears to be allergic to soybean oil and I have reason to suspect that soy lecithin may also be a problem. Anecdotally, I’ve read blogs by people that react to these and corresponded with others that have. Working out if you’re allergic to soybean oil and/or lecithin can be a lengthy and frustrating process that often comes back to food diaries, trial and error, and consulting with a medical specialist.

Part of the problem with these two products is the possible variations; one day a food product might contain sufficient ppm of soy protein to trigger a reaction and another time it might not. For instance, leaving aside questions of general health, take the following example:

One Friday night you go to the supermarket and purchase (A) ice cream and (B) ice cream cones; both of these products contain soy lecithin as emulsifiers.

  • How much soy protein is in the separate batches of lecithin in products (A) and (B)? What if one has 18 ppm and the other has 1650 ppm?
  • What percentage of each product is made up of soy lecithin? What if one product is 5% and one product is 0.5%?
  • How much of each product are you consuming? What if your ratio of ice-cream to cone is 4:1 ?
  • What if the only reason you have a reaction is because of allergenic loading; i.e. you’re not actually reacting to (A) or (B) but rather to the combined exposure as a result of (A) + (B)?

Maybe you react and maybe you don’t. Maybe you buy exactly those same products (from exactly those same manufacturers) a month later and you do react because one or more of those questions above has a different answer.

Final conclusion: Food allergies suck.

I feel like I should make some off-the-cuff remark like “Food allergies suck (but not as much as vampires)” just to lighten the mood but the reality is that they do. Kia kaha, stay strong.


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