Food Contamination & Food Intolerance Processed fruit or vegetable juice has anti-browning chemicals that may trigger asthma.   Sometimes, food contamination and food intolerance may result in symptoms similar to food allergy. Examples include:   1. Milk intolerance     Some people experience food intolerance to milk due to deficiency in lactase, which is an enzyme secreted by the lining of the gut for digesting the lactose in milk. If a person does not have enough lactase, the lactose in milk products cannot be digested by the body and is consumed by bacteria in the gut instead, releasing some gas. The person would experience bloating, abdominal pain and sometimes diarrhea.     2. Intolerance to food additives (colour, flavouring, anti-browning agents etc.)     An adverse reaction may be due to certain products that are added to food to enhance taste, provide colour, or protect against growth of micro-organisms. These include:     Artificial colouring - Yellow dye number 5 can cause hives, though rarely. Monosodium glutamate (MSG) is an artificial flavour enhancer. When consumed in large quantities, MSG can cause flushing, sensations of warmth, headache, facial pressure, chest pain or feelings of detachment in some people. Anti-browning chemicals called “sulphits” (or “sulfits”) can occur naturally in foods or are added to processed food to enhance crispness, prevent mold / bacterial growth, or delay the browning of pre-packaged fruit / vegetable products. Sulphits in high concentrations may trigger an asthma attack for asthmatic patients. After reacting with gastric acid in our stomach, sulphits can give off a gas called sulphur dioxide. Some of the gas is regurgitated and inhaled by the asthmatic, causing irritation to the respiratory tract and even severe bronchospasm, a constriction of the lungs. (more) Anti-oxidants - An aniti-oxidant called ascorbic acid is used in butter, fats and oils to prevent them from going rancid. Anti-oxidants may trigger rashes, hives and tight chests. Sweeteners (e.g. aspartame) - These are used as a sugar substitute in low-calorie foods. Aspartame may cause rashes or hives, dizziness, hallucinations and headaches. Other symptoms include throat irritation, wheezing, a worsening of eczema, stomach pains , vomiting and diarrhoea.         3. Histamine toxicity     There are some natural substances, such as histamine, that can occur in foods and stimulate a reaction similar to an allergic reaction. For example, histamine can reach high levels in cheese, some wines, and in certain kinds of fish, particularly tuna and mackerel, due to bacterial contamination. Eating these food may result in reactions called histamine toxicity, which has symptoms like an allergic reaction to food.         4. Bacterial contamination     Some food may be contaminated with micro-organisms such as bacteria and toxins produced by them. Eating such contaminated food may result in food poisoning, which has symptoms very similar to food allergy.