Symptoms can range from mild to severe and include: abdominal pains, cramps and bloating, flatus, diarrhoea and vomiting. The severity ranges from individual to individual, which may be provoked by lesser or greater quantities of the food substance that the body is unable to process or digest.

Symptoms of food allergy include rash, swelling of the eyes and airways and difficulty breathing.

Sometimes it is easy to pinpoint the underlying cause. For example, if milk always triggers symptoms, then it is likely that you have lactose intolerance. However, if the link is unclear, or there are doubts about the exact causation, you should seek specialist medical attention. 

There is no specific food associated with intolerances.However, there are groups of sugars or substances responsible for these intolerances. Commonly these include the FODMAPs, of which Lactose, Fructose, and Sucrose are the commonly recognized sugars. 

Intolerance refers to the body’s inability to digest or has difficulty processing the substance, which can cause symptoms such as bloating, loose stools, cramps or increased gas production. Patients with lactose intolerance have difficulty digesting milk and dairy products. Normally, the digestive system produces an enzyme to break down lactose, the main sugar found in milk. For patients with lactose intolerance, there could be a lack of enzymes produced by the body or the enzyme does not function properly. This results in excessive lactose remaining in the digestive system, where it is fermented by bacteria to produce various gases, which causes the gastrointestinal symptoms of lactose intolerance.

A food allergy is caused by the body’s immune system being hypersensitive to a certain food. Whilst one can be allergic to any food, some foods are more allergy-causing, for example nuts and seafood.

Genetics play a major role in allergies, and it is common for allergies to run in families and are often hereditary. 

On the other hand, food intolerances can be both genetic and acquired. For example, having a severe episode of gastroenteritis can result in damage to the lining of the intestines and can result in reversible transient lactose intolerance.  

One of the commonest food intolerances is lactose. Patients with lactose intolerance have difficulty digesting milk and dairy products. Normally, the digestive system produces an enzyme to break down lactose, the main sugar found in milk. For patients with lactose intolerance, the enzyme is not produced enough by the body or does not work properly. This results in excessive lactose remaining in the digestive system, which gets fermented by bacteria to produce various gases, which causes the gastrointestinal symptoms of lactose intolerance.

For the FODMAPs, testing is available using a breath test. This is where the patient is fed the pure sugar in question, and breath is collected to test for a spike in gas production. The patient is also observed for symptoms. A positive test would indicate that the patient has an intolerance and cannot effectively digest the food substance.

Diagnosis of allergies would involve a patch test and blood test. Patch or skin prick tests are where the food substance is injected below the skin to see if the body’s immune system mounts a reaction. A blood sample may be drawn to test for antibodies to a particular food.    

There is no treatment for food allergies. In severe cases, an immunologist may be able to help with desensitisation treatment.

There is also no cure for food intolerances. Treatment depends on how severe the condition is. In general, you can utilise self-help home remedies to avoid or control the symptoms. Using lactose intolerance as an example, self-help home remedies would include consuming less dairy food like milk, cream, cheese, butter, yoghurt and ice cream. Patients with severe lactose intolerance may have to read the labels of the foods they eat to avoid lactose. Taking the appropriate enzyme supplement before eating can also help to digest lactose in the diet. For patients who are completely avoiding dairy foods, calcium or vitamin D supplements should be considered