There are literally hundreds of food additives including colors, flavors, spices and preservatives, that are added to the foods we eat everyday in order to enhance the flavor, change the color or texture, or to increase the shelf-life of the food product. Most individuals will come into contact with many of these additives every day as a part of a normal, balanced diet. We often don’t think about - or pay attention to - the potential allergy issues associated with these additives.
Like anything we ingest, there is always the potential for an adverse reaction, including both immunologic (allergic), and non-immunologically (non-allergic) reactions. The range of symptoms attributed to food dyes, spices, and additives is diverse, but may include classical allergy symptoms such as anaphylaxis, asthma, hives, rash, and nasal symptoms, as well as non-allergic symptoms such as headache, behavioral changes, digestive difficulties, and fatigue.
In general, dyes and additives very rarely cause a true allergic reaction. There is much circumstantial description of symptoms attributed to various additives or colorants, but controlled trials that have examined this issue have been inconclusive in establishing a cause and effect relationship. There is, however, evidence supporting the fact that some additives can provoke an antibody mediated reaction that would be considered an “allergy”.
The following is a summary of agents that have shown the most convincing evidence of true allergic reactions, and agents which cause symptoms that are not the result of an allergy, and are best characterized as an adverse reaction.
Two agents in particular have demonstrated proof that a true allergic reaction can result from their use. One of these is Carmine, a crimson/wine red/pink natural color derived from the pulverized, dried bodies of female Coccus cacti insects.
The red dye contains residual insect body protein, and this has been shown to cause a true allergy as mediated by a specific antibody. Carmine has been linked to asthma induced from inhalation of the dry powder. Interestingly, this has been reported to occur primarily in men.
Anaphylaxis, on the other hand, has been shown almost exclusively in females who presumably become sensitized to this agent through its use in makeup and cosmetics. As a result of this sensitization, ingestion of carmine containing items can subsequently result in serious allergic reactions.
The other agent which can induce an allergic reaction is Annatto. Annatto is a yellow colored powder derived from the seed of the Bixia orrellana bush. Most people have been exposed to annatto, as it is used to color dairy products, as well as confections, soda, and processed goods. This is the agent responsible for the distinctive color in cheese, and butter, and macaroni. Outside of the U.S. it is used in meats as well.
Annatto allergy has been demonstrated on standard allergy scratch tests, as well as specialized research laboratory tests, in sensitive individuals.
Other natural colorants that have shown more limited evidence of true allergic reactions include saffron (asthma, anaphylaxis), anthocyanins in grapes (anaphylaxis to grape containing products including certain wines), and paprika.
There have been several clinical trials that have looked at whether colorants can cause symptoms including allergy and behavioral changes. None of these trials have shown any evidence that such an association exists, though anecdotally, there are many parents and individuals who are convinced that one does indeed exist.
Yellow dyes were implicated in some of the earliest reports of possible colorant induced allergy. Tartrazine (FD&C Yellow #5) has been linked to reports of chronic hives, asthma, and cross-reactivity in aspirin allergic patients. Chronic hives was studied in oder to determine if chronic hives could be “unmasked” by allergy to tartrazine. Again, no evidence exists that supports such associations. In fact, in cases where the dye appeared to cause allergy symptoms, further analysis determined that the symptoms may have resulted from confounding or coincidental causes, such as withholding chronic medication.
Tartrazine has also been shown to have no clinical cross reactivity in inducing hives in aspirin/ibuprofen allergic patients, and consequently, there is no contraindication to this dye in an aspirin sensitive patient. Its role in inducing asthma also has not been supported by medical evidence. One randomized, placebo controlled trial did suggest that very high doses (>10 times that encountered in use in a medication dose) of tartrazine may induce hyperactivity in children, though this effect was not seen at low doses commonly used commercially in foods or medicines. Contact reactions to tartrazine, as well as other certified dyes, are a recognized entity.
Other certified colors questionably linked to allergy include FD&C#40 (Red 40) and FD&C yellow #27.
Since spices are derived from plants, there are some case reports of symptoms resulting from spice allergy. Many of these spices share the very same proteins to those found in certain pollens, and have theoretical ability to induce a phenomenon called the “oral allergy syndrome”, which rarely results in a serious allergic reaction. Occupational inhalation of several spices has been associated with reports of asthma attacks.
Sesame and other similar seeds such as poppy, commonly used as spices, share common allergenic proteins and are increasing in the U.S. as a cause of serious allergic reactions. Sesame and other seed allergies are very clearly antibody mediated, with reliable cutaneous as well as blood tests available to aid in the diagnosis.
Because spices often have aromatic properties, contact with the skin can induce irritation through direct tissue damage. Spices can also cause contact dermatitis similar to a Nickel allergy or poison ivy type reaction. In general, spice induced reactions are uncommon, and anaphylaxis or major allergy symptoms from spices are rare. Testing to these agents is best done with fresh specimens, but this is a non-standardized process, and the test may irritate the skin making interpretation difficult. Avoidance of spice agents is also a somewhat daunting task, given their common use in the American diet.
BHT and BHA are two popular synthetic antioxidants used in foods to help preserve texture, especially in animal fats. In 1958, they were declared generally regarded as safe for use in food. Animal toxicology studies have shown BHT may induce immunologically mediated lung damage and fibrosis, but alternatively, both BHT and BHA have been shown to be protective for certain types of malignancy, and possibly possess anti-atherosclerotic properties. These effects have not been demonstrated in humans. In case reports, both have been implicated in inducing asthma and chronic hives, but other studies have not supported this association. Otherwise, BHT/BHA is linked to contact reactions.
Monosodium Glutamate (MSG) is a very controversial additive found commonly in Chinese food, though it is certainly not limited to this type of cuisine. In 1968, a physician published a letter to the editor of The New England Journal of Medicine detailing an odd constellation of neurological symptoms experienced when eating at a Chinese restaurant, suggesting that MSG could be the causative agent. Thus, a major controversy which still exists today was sparked.
At high doses in humans, nausea can result and several case reports suggest that MSG exacerbated asthma. Others have suggested that hives may be attributed to MSG. Though difficult to perform, several challenge studies have shown no evidence of an MSG symptom complex, or even symptom development. Asthma studies showed a similar lack of evidence to support an association with MSG, as have the few studies done to explore the role of MSG in provoking chronic hives. MSG causing headache has been studied, but was not shown to have a significant association, despite widespread belief to the contrary.
In summary, MSG probably does not cause symptoms based on controlled studies, but high doses may infrequently be associated with symptom development, especially headaches.
Sulfites are widely used as a preservative. Unlike many other additives, sulfites do have a well defined role as provoking asthma, although not as commonly as originally thought. Asthma has been demonstrated after sulfite administration in several studies, and fatal reactions have been described. The association is much better established in adults than in children. It is not known exactly how sulfites trigger asthma, but positive skin tests have occurred, implying that it is an antibody mediated reaction.
Sulfites affect only about 5% of asthmatics and tends to be more common in those with more severe and persistent asthma. Most experts recommend a controlled challenge to confirm symptoms after a history of a reaction. In such individuals, avoidance of sulfite containing items is strongly encouraged. Interestingly, epinephrine devices (EpiPen® or Twinject®) do contain small amounts of sulfites, but the medication is still effective (and highly recommended) to treat a sulfite induced reaction.
Sulfite sensitive individuals with asthma do have a certain degree of tolerance to sulfites, abut certain foods are more dangerous than others, especially acidic foods. Foods with less than 10-50 ppm sulfites are far less likely to induce a reaction, but this has not been readily tested. Avoidance is highly recommended, as is confirmation of the reactivity with an oral challenge under the watchful eye of an allergist.
These items are common preservatives in wide use in food and other products. Both have been implicated in chronic urticaria, but there has been no evidence to suggest an association with asthma. Paraben use in local anesthetics has been attributed in systemic reactions, and parabens are known to cause contact dermatitis.
It is very difficult to identify the particular food additive in question as the true culprit in precipitating a reaction, especially since there are many other items that could also be responsible. of great help to an allergist evaluating such a complaint is a clear, concise history of exposure to the particular item consistently causing symptoms.
If symptoms are intermittent despit