How do you know if you have a food allergy?

Some people develop a hypersensitivity, they may sneeze a lot, having coughing attacks, breathing may be impaired, worse case senario would be fainting, hyperventilating, seizures, coma etc.

Sink break outs can occur, bloating, bowel problems, reflux, headaches, aches and pains in the body (usually muscular), just to name a few.

Craving for a food badly can indicate you are allergic to it, since on a nutritional basis your body is desperately trying to take certain nutrients on board that are lacking in the diet.

A full dietary assessment is required.  Many allergies can be resolved with change of diet and correct nutritional supplements given to balance out deficiencies.
http://lyncravencorporatehealth-naturopath.com/documents/assimilate.pdf

Lyn has identifed many of the common symptoms suffered by people who have food intolerance/allergy.

It is important to note that a food allergy involves an immune response and is often immediate such as a nut allergy causing anaphylaxis. Whereas a food intolerance tends to be less immediate and doesn't involve the immune system.

To diagnose an allergy Skin Prick testing and RAST testing are the gold standard for diagnosis allergies, along with food challenges conducted by an experienced Allergy Dietitian or GP. An individual may have a positive reaction on Skin Prick Test however still able to consume the food.

If you are concerned you may have food intolerance/allergies I recommend contacting your local GP and specialist allergy Dieititian trained in food allergy.

The most common form of food allergy is usually caused when the body produces an “allergic antibody ” ( medically called IgE) to a food.  If the trigger food is eaten, then people who suffer from food allergies usually develop a local response such as an itch or tingling in the mouth.  If the reaction is severe they can go onto develop symptoms of a more severe allergic reaction such as difficulty breathing, asthma or symptoms of low blood pressure such as fainting or collapse. This is called anaphylaxis.  Some people have other symptoms such as nausea, vomiting or a rash or flushing on their body.  All these symptoms usually occur within minutes of eating the food and are rarely delayed longer than an hour or so of eating the food.  These sort of food allergies are those that develop the most severe reactions and can, rarely be associated with death.
These types of allergies are the ones that most allergy specialist doctors see and are the ones requiring an emergency treatment . These severe types of reaction are usually investigated by looking for the ‘allergic antibody ’ in the blood or by skin tests. 

If you have any of these severe symptoms it's really important to get specialist medical advice to make sure exactly what the food trigger is and to have an appropriate emergency plan. 

In adults, food allergy tends to cause predictable, stereotyped reactions after eating a particular food. This is usually IgE-mediated, meaning it activates the arm of the immune system affiliated with these antibodies. The most useful clue is the pattern: symptoms usually occur reproducibly after eating the food, often within minutes and usually within a few hours.

Symptoms can include hives, swelling of the lips, eyes or face, vomiting, abdominal pain, wheeze, throat tightness, dizziness, fainting or collapse. Severe reactions involving breathing symptoms, throat symptoms, low blood pressure, collapse, or symptoms affecting more than one body system should be treated as possible anaphylaxis and need urgent medical attention, including adrenaline.

A clinical immunologist or allergist will try to determine whether the symptoms fit with food allergy, and distinguish this from other conditions such as coeliac disease, food intolerance, or non-allergic reactions to food.

The most important part of diagnosis is a careful history. If there is a suspicious food trigger, further testing may involve skin prick testing, where small amounts of allergen are introduced into the top layers of the skin, or blood testing for specific IgE. These tests help refine the probability of food allergy, but they do not diagnose food allergy on their own.

The gold standard diagnostic test for food allergy is a supervised food challenge, where the person eats the food in controlled and safe conditions. This is particularly useful when the history is unclear, or when the food is nutritionally important. Broad food allergy panels without a convincing history can be misleading and may lead to unnecessary food avoidance, so they are generally best avoided.

Some food allergy does not follow this pattern exactly - such as in wheat dependent exercise induced anaphylaxis or mammalian meat allergy. Therefore, it is very important to see a specialist allergist who can provide a comprehensive service.