A wide range of additives are used in the food industry. Many symptoms have been attributed to individual food additives, but a causal relationship is generally difficult to prove.
Adverse reactions to additives seem to be rare, but may well be underdiagnosed, due to a lack of recognition of the offending agent.
Reactions to additives are due to several different mechanisms, including receptor-mediated, irritant, toxic, immunologic, or psychologic. Classic allergic IgE-based reactions have been demonstrated to some additives derived from natural sources (e.g. annatto, carmine, saffron and erythritol). However, most reactions to additives are not IgE-mediated.
Commonly food additives are shown below (taken from Wilson BG et al. Ann Allergy Asthma Immunol. 2005;95:499–507)
Antioxidants: Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate, tocopherols
Dyes and colorings: Multiple natural and artificial agents, including azo dyes (tartrazine) and non-azo dyes (erythrocine)
Emulsifiers: Gums (e.g. arabic, tragacanth, karaya), lecithin, propylene glycol
Flavorings and taste enhancers: Monosodium glutamate (MSG), spices (e.g. aniseed, cinnamon, coriander, cumin, fennel, flaxseed, ginger, hops, mustard, nutmeg, red pepper, white pepper)
Sweeteners: Artificial (e.g. acesulfame, aspartame, saccharin, sucralose), Natural (e.g. corn syrup, fructose, glucose, sorbitol, stevia, sucrose, xylitol)
Preservatives and antimicrobials: Benzoates, citric acid, nitrates and nitrites, parabens, salicylates, ascorbic acid, sulfiting agents
Stabilizers: EDTA, gums (e.g. carrageenan, guar, others), waxes
Frequency in population and natural history
Few studies have examined the prevalence of adverse reactions to additives. Prevalences of below 1% in adults and around 2% in children are reported, with a higher prevalence in children with other allergies (2% to 7%).
Underreporting of these reactions is probable due difficulty in recognition or verification.
Skin reactions are common, such as rashes, itching, hives and flush. Abdominal cramps or pain, nausea, diarrhea and swelling or itching in the mouth, muscle and joint pain, difficult breathing, cough, runny nose, headache, irregular heartbeat, blood pressure changes, dizziness, changes in skin sensation, headache can also occur. Anaphylaxis (a sudden and strong life-threatening allergic reaction affecting the heart, circulation and breathing) is rare, but possible.
Testing and diagnosis
The medical history of food reactions is most important, looking for a common factor (the additive) between seemingly unrelated foods.
A hypersensitivity reaction to an additive can be suspected when there is a reaction to several unrelated foods or to a specific food when commercially prepared but not when prepared at home. Reactions to food proteins are more common than reactions to additives. Consequently, exclusion of a reaction to an unsuspected (“hidden”) food protein (e.g. milk, meat, egg) is important before a reaction to additives is diagnosed.
Skin testing can be helpful in detecting sensitivity to natural additives, but is unreliable for synthetic additives. In case of suspicion of a reaction to a specific additive, an elimination test with re-exposition is possible. Double-blinded placebo-controlled testing remains the desirable, but unpractical gold standard.
Information regarding all the different possible synonyms and names and careful avoidance of the identified additive are the mainstay of treatment.
In case of severe reactions, patients should wear a medical identification tag and carry a self-injectable epinephrine kit at all times. Minor reactions can be treated symptomatically with antihistamines.