Many of today’s food manufacturers add additives to their products to enhance the flavor, improve the nutritional content, extend shelf-life or just change the color, texture and appearance of the product. Though these additives are safe for the vast majority of people, a small minority may experience a reaction to the additives – though the existence of additive sensitivity is a hotly debated issue itself. Statistics vary, but the U.S. Food and Drug Administration (FDA) estimates 1 percent to 3 percent of adults and 6 to 8 percent of children may experience some sort of sensitivity to food additives. Only one type of additive, sulfites, are known to cause allergic reactions in some people.

An allergic reaction to sulfites is very rare, though symptoms can include hives, stomach cramps, nausea, difficulty breathing and even life-threatening anaphylactic shock. Sulfites are commonly used for preservation in many kinds of food (e.g., wine, dried fruits), though the use of the additives is strictly limited by the FDA. Sulfites also occur naturally in a variety of foods (e.g., salmon, tomatoes, onions). 

Some physicians and clinical researchers deny the existence of additive sensitivities other than sulfite allergies. Though widely reported, no conclusive clinical data exists to confirm them as a medical condition. More studies and research are needed before the medical community reaches a final decision on food additive sensitivities.

Reactions caused by additives other than sulfites are food intolerances, not true allergies. Intolerance occurs when the body has difficulty digesting a certain food. An allergy is caused by the immune system's perception that a substance is a foreign invader. An intolerance to additives is reported to cause temporary symptoms such as headache and abdominal pain, especially when the additive has been consumed in large amounts.

Some of the most common additives that have been associated with sensitivities include:

• Sulfites. FDA-regulated food additives. According to the FDA, about 5 percent of asthmatics are sensitive to sulfites. Sulfites are capable of causing food allergy reactions in some people. By law, sulfites cannot be sprayed on vegetables and fruits meant to be consumed raw, but are used in some processed foods and to preserve seafood. Sulfites appear in wine and, to a lesser extent, beer and other alcoholic drinks. They must be declared on the label, if there is a detectable amount in the finished food. The FDA’s regulation defines a detectable amount of sulfite to be 10 parts per million.
  
  
• Monosodium glutamate (MSG). A common preservative and flavor enhancer, especially popular in Asian dishes. When consumed in large amounts, MSG has been reported to cause flushing and headaches.
  
  
• Aspartame. An artificial sweetener commonly found in soft drinks, chewing gum, tabletop sweeteners and 6,000 other food products. Aspartame is considered safe by the FDA but some people have reported a wide number of allergy-like symptoms, some of which may be due to an intolerance. Certain people, such as those with the genetic disease phenylketonuria (PKU), those with advanced liver disease and pregnant women with hyperphenylalanine (high levels of phenylalanine in blood), may not be able to digest aspartame.
  
  
• Benzoic acid. A preservative frequently found in processed foods, such as juices, chocolate, chewing gum, nut flavorings and baked goods.
  
  
• Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Commonly used to prolong the life of fats, oils and oil-containing foods, such as potato chips, vegetable oils and cereals.
  
  
• Tartrazine. A yellow food coloring, also known as FD&C yellow number five.
  
  
• Cochineal extract (also known as carmine dye). A color additive used for centuries in foods, drink and cosmetics. On food labels, it may appear by name, but other labels may only list it as color added or artificial color.
  
  
• Nitrates/nitrites. Used to prevent botulism and enhance the flavor of red meat, poultry and meat/poultry products (such as hot dogs, salami, bacon, turkey, chicken and ham).
  
  
• Parabens. A common preservative used in many foods (e.g., mustard, processed vegetables, mayonnaise, salad dressings, soft drinks, jellies and jams, syrups), drugs (e.g., eye, ear and nose drops, local anesthetics, rectal/vaginal medications) and cosmetics (e.g., makeup removal products, blushes, lip sticks, mascaras and eye shadows, nail products).

Food additive sensitivities are usually reported to occur when an additive in a food is ingested. However, some additives used in foods are also used in cosmetics. Direct contact with these substances on the skin may also be able to produce a reaction.  

The FDA closely monitors the additives currently on the market and keeps track of the many complaints it receives on adverse food reactions. Because of the FDA’s work, food manufacturers are currently required to list all additives by name on their product’s packaging. The FDA also maintains a Generally Recognized as Safe (GRAS) list that includes foods that have been in use for five years without any known problems.

Some individuals who report suffering from additive sensitivities have worked with a physician or a physician-recommended dietician to identify and avoid problematic additives. For those patients who have already identified problem additives, new FDA requirements for the labeling of foods make it easier to quickly check to see if a potentially problematic additive is present.

Because of limited clinical data available on additive sensitivity, it can be difficult to determine if an added ingredient triggered actual symptoms. Therefore, the treatment of additive sensitivities can be more involved than treatment of food allergies. People who find they are sensitive to certain additives are encouraged to pay close attention to what they eat.