Certain types of food, such as nuts or shellfish, can trigger directly an allergic reaction in some people. Eating other foods, such as bananas, can indirectly facilitate or intensify an allergic reaction (banana protein chemically resembles the latex protein, a common allergen). Popularly, food intolerances may be incorrectly termed allergies.
Allergy symptoms include hives, lip swelling, itching, shortness of breath, wheezing, chest or throat tightness or even loss of consciousness, often within minutes of food ingestion. For those most sensitive to allergens, eating just one five-thousandth of a teaspoon can produce a fatal reaction. One problem is cross-contamination, unintentional residue left on utensils or equipment used to make separate batches of food products.
True allergic reactions occur within minutes to an hour of contact with the allergen. This differentiates them from pseudo-allergic reactions, which do not involve the immune system and can occur up to 48 hours after contact with the offending substance. Some people use the term intolerance to refer to some of the non-immunologic adverse reactions to foods.
Up to 8% of children less than 3 years and approximately 2% of the adult population experience food-induced allergic disorder; this amounts to 2.5 to 5 million people in the USA, for example. 30,000 residents of the USA are hospitalized every year after eating allergenic foods, and 200 of them die.
Foods that most commonly cause allergies include: cow's milk (especially in children), eggs, fish and shellfish, walnuts, cashews, peanuts, soy protein, legumes and wheat. As the first example, cow’s milk is noted as one of the first foods given to babies and subsequently is one of the first types of allergies to appear in children (gastrointestinal and skin problems were reported as far back as Hippocrates). Respiratory problems are one of the first symptoms of cow’s milk allergy (CMA). One study notes several symptoms, including: rashes or redness; itching; abdominal pain and bloating; nausea, vomiting and diarrhoea; coughing, wheezing and asthma symptoms. As symptomology from milk consumption become more frequently reported, there are incidences of anaphylactic shock and slowed physical growth in children.
A page in an article covered by JAMA Network in 19949 noted that cow’s milk allergens in infants range from 0.5 to 7.5 percent but may be as high as 25 percent in some patient groups, and it’s often missed due to unspecified symptoms and different areas of the world. Another study noted that cow’s milk more frequently being given to infants in lieu of breast milk may explain part of the increase being seen.
A 2001 sample survey by the US Food and Drug Administration (FDA) found that one quarter of the companies failed to list all ingredients on their products, and nearly half did not check to make sure labels showed all of the ingredients. Of all the products sampled, 25 percent had undisclosed traces of peanut, and 11 percent had unlisted traces of egg, another common allergen. The FDA requires the listing of even trace amounts of foods that can set off allergic reactions.
Up to 30 percent of the public think they have a food allergy to milk, fruit, juices or tomatoes. In fact, they have intolerance to certain foods—lactose intolerance for instance.