These days we hear a lot about food allergies. Rates are rising and estimates suggest that in developed countries as many as 8% of the population may have one or more. But what exactly are they?
Food allergies are caused by our immune systems: they develop an abnormal sensitivity to certain foods and respond to these as though they were pathogens. The resulting symptoms may range from mild discomfort all the way up to life-threatening. They usually appear within minutes of eating the problematic food, but can be delayed for an hour or more.
Allergies occur when a misfiring immune system responds to the molecules or proteins contained within a particular food by releasing a type of antibody called Immunoglobulin E, or IgE. This in turn triggers the release of histamine and other neurochemicals, and these in turn kickstart the inflammatory response used by the body to fight off pathogens.
Food allergies should not be confused with food intolerances, also known as food sensitivities. Although they can be triggered by many of the same foods, intolerances are centred in the digestive system rather than the immune system. Food intolerance can produce uncomfortable symptoms and indigestion but these rarely require medical intervention.
Types of food allergy tests
A number of food intolerance and allergy tests are available to detect or confirm the presence of allergies. If a person has a clear history of allergic reactions to particular foods, that might be sufficient for an official medical diagnosis.
Other options include the skin prick test, in which small quantities of particular foods are applied to a person’s skin to see if an allergic reaction develops. Also common are blood tests to detect the presence of those pesky antibodies.
Common types of food allergies
So what allergies can these tests show up? The following are the most commonly experienced allergies and the type of symptoms that may be experience, although it should be noted that symptoms are very individual:
Despite the name, peanuts are not actually nuts. Instead they are a legume, and therefore related to beans. Typical symptoms of a peanut allergy include sneezing, stomach pain, diarrhoea, eczema, and hives.
Peanut allergies can also cause anaphylaxis, the most severe and potentially life-threatening form of allergy. Anaphylactic shock can be indicated by:
- Falling blood pressure
- Facial swelling
- Cardiac arrest
People prone to anaphylaxis typically carry an ‘epi pen’ with them. These medical devices, which are issued by the NHS, allow sufferers to quickly inject a dose of epinephrine, otherwise known as adrenaline. Consumption of peanut products during pregnancy and early infancy is the most effective preventative measure.
Soya is also a legume and another very common allergy trigger. Typical reactions include indigestion, wheezing and erythema – reddening of the skin.
Dairy allergies are triggered by the proteins in cow’s milk. According to the Asthma and Allergy Foundation of America, milk is the commonest cause of allergy in the United States, and it is also widespread in other parts of the world. Milk allergies are associated with such unpleasant symptoms as:
- Itching and dermatitis
- Facial swellings
- Stomach pain
- Wheezing and hoarseness
- Nasal congestion
At their most severe, milk allergies can cause intestinal inflammation and anaphylactic shock.
Wheat allergies can be triggered by eating wheat or just by exposure to the grain. Wheat contains multiple proteins with allergenic properties for sensitive individuals. Sufferers may experience such symptoms as cramps, swelling, nausea and hives. Severe wheat allergies can also cause anaphylactic shock, so sufferers may need to carry an epi-pen with them.
Coeliac disease is not an allergy, but a distinct auto-immune condition triggered by the wheat protein gluten.
A sensitivity to shellfish may cause some of the same reactions associated with the allergies listed above, including eczema or hives, excessive itching, facial swelling, wheezing, nasal congestion, dizziness and shortness of breath.
Sufferers may react to all shellfish or only to specific types.
What causes these allergies?
Allergies have a variety of causes. They can be inherited from your parents but they have also been linked to low levels of vitamin D or to being overweight. There is also the ‘hygiene hypothesis’.
As the name suggests, this began as a theory that allergies develop in children when they have grown up in an overly clean environment, because children’s immune systems require training, and learn to trigger in response to infection or disease via exposure to a sufficient quantity and variety of germs. If this does not occur, the hypothesis went, their immune systems misfire, triggering in response to harmless foods or other substances the child may come into contact with.
Since then, the hygiene hypothesis has evolved and it is now believed that exposure to a wide variety of healthy microbes and gut bacteria is key, rather than germs specifically. Such exposure can be provided via an active lifestyle with plenty of outdoor play and social activities. A healthy diet and minimal exposure to antibiotics also help.
How to discover your allergies
If you have any health concerns and feel you might have a serious food allergy, your first port of call should be your doctor. Once they have ruled out anaphylaxis, most GPs will refer patients with suspected allergies to an allergy clinic for further testing.
Another, quick way to discover what – if any – food allergies you have, is to take an at-home food allergy test. Collect a blood sample via a simple finger prick and send this back for a detailed analysis.
The test will reveal the presence or absence of IgEs triggered by 38 different foods:
- Grains: wheat, oats, barley, maize and rice
- Legumes: green beans, peanuts and soya
- Dairy foods: egg, milk
- Seafood: cod, tuna, salmon and shrimp
- Meat: beef, lamb and chicken
- Fruits: banana, kiwi, mango, pineapple, strawberry, peach, orange and apple
- Vegetables: tomatoes, onions, potatoes, mustard, garlic, celery, carrots and ginger
- Nuts: almonds, cashews, hazelnuts, walnuts and sesame seeds
You will also get a reading of total IgE in your blood sample, this is non-specific but may indicate a recent allergic reaction. Armed with this information you will be able to make truly informed decisions about your diet and protect your health.