Individuals who have exhibited a history of allergies, eczema or asthma are more likely to have a food allergy. These individuals are also more likely to have a severe or life-threatening reaction, such as anaphylactic shock.

Several related conditions may be mistaken for a food allergy. These include:

• Food intolerances. These conditions involve the body’s inability to breakdown specific food substances (such as lactose with milk intolerance) – rather than an allergic response to the food in question. With lactose intolerance, for example, a person lacks sufficient amounts of the enzyme lactase, which makes it possible to breakdown the lactose in milk. Symptoms of food intolerances generally involve discomfort, such as stomach cramps, bloating, diarrhea or gas. However, they are very rarely severe or potentially life-threatening. Also, people with food intolerances can often enjoy small quantities of the problem food without risk. People with food allergies need to completely avoid even trace amounts of the problem food.
  
  
• Food poisoning. Food poisoning can also imitate an allergic reaction. But, while the symptoms might appear similar, the body is not producing an actual allergic reaction in these instances. Rather, it is responding to harmful bacteria or other toxins within contaminated or spoiled foods. Reactions can be severe and may therefore be confused with food allergies.
  
  
• Additive sensitivity. Food additives are substances added to food for better preservation, taste and color. Some people have reported experiencing reactions to certain additives when ingested (e.g., MSG). However, there is currently no clinical proof that confirms the existence of this type of sensitivity. More research is needed on this subject before the medical community can confirm or reject this condition.
  
  
• Irritable syndrome bowel. A disorder in which the large intestine (colon) does not function normally, leading to cramping, abdominal pain, bloating, constipation and/or diarrhea. Because specific types of food will sometimes trigger irritable bowel symptoms, this condition may be confused with a food allergy.
  
  
• Other gastrointestinal conditions. Some kinds of cancers, inflammatory bowel disease and ulcers of the gastrointestinal tract can produce symptoms similar to those experienced with food allergies. These symptoms can include vomiting, diarrhea or cramping abdominal pain that gets worse when eating.
  
  
• Stress or psychological issues. Though the relationship between stress and allergy symptoms is not entirely clear, some individuals will feel sick simply by thinking about a certain type of food.

Cross-reactivity can occur when a person who already has one known type of food allergy seems susceptible to a chemically related food or other allergen. For example, someone with a strong reaction to wheat may also be allergic to oats. For individuals with severe allergic reactions, a physician will often suggest avoiding related food types.

Cross-reactivity can also occur with nonfood allergies. For instance, most people with latex allergies react only to the natural latex protein found in latex products. However, some of these individuals find they are also allergic to fresh fruits, vegetables and nuts. This occurs because the protein in latex is so similar to the proteins found in the fruits, vegetables and nuts that the body is unable to distinguish between them.

Other conditions associated with food allergies include:

• Oral allergy syndrome. This cross-reactive condition involves an allergic reaction being triggered in an individual who is allergic to pollen or another airborne allergen. Fresh fruits, vegetables and nuts can all have allergens similar to some airborne allergens. When these foods are eaten the allergens come into contact with the lining of the mouth and throat, resulting in itching or swelling of the lips, tongue or throat. In this case, the immune system confuses the allergens in the fruit with the airborne allergens.
  
  
• Exercise-induced food allergy. An exercise-induced food allergy is usually triggered when an individual exercises after eating a specific kind of food. People who are susceptible to this kind of reaction can avoid problems by eating at least two hours before exercising.
  
  
• Infantile colic. This condition is sometimes associated with food allergies. An allergy to milk or soy may be responsible for up to one in five cases of colic in infants. This likely comes as a result of the immaturity of the immune system in infants with these allergies.