This is a fascinating subject I think. I had a friend who thought they were intolerant or allergic to loads to things, turned out he was just lonely! As soon as he got a girl he was chomping away with the rest of us! But seriously, genuine food allergies affect about one to two people in every 100 in the UK. Food allergy is sometimes confused with food intolerance or food poisoning. These can make you feel ill but they aren't usually harmful in the same way that a true food allergy might be.
Foods that cause allergies include peanuts, tree nuts (Brazils, almonds, cashews, hazelnuts, walnuts and pecans), fish and shellfish, cows' milk, eggs, soya and wheat.

The incidence of food allergies in young children are more common than in adults, but many children outgrow them by school-age. It's possible, however, to develop a food allergy as an adult, even if you never had allergies as a child.

It is true to say that f you have one food allergy, you may also react to other foods. For instance, if you're allergic to prawns, other shellfish may also affect you. People with hay fever or an allergy to latex may also find their allergic reaction crosses over and happens with certain foods. This is called cross-reactivity.

If you have an allergy, it means that your body's immune system reacts to an allergen - a substance that causes an allergic reaction. An allergic reaction happens when your body's immune system mistakes the allergen, for example nuts, for a harmful invader and produces antibodies. This is known as sensitisation and may not cause symptoms. However, the next time you eat the food, the antibodies are ready to react with it. This causes your body to release chemicals, which leads to a range of physical symptoms known as an allergic reaction. Allergens aren't usually harmful and most people aren't sensitive to them.

Some food allergies result in immediate, severe and even life-threatening symptoms (such as severe peanut allergy), whereas others cause symptoms that may take longer to develop (for example, gluten allergy, also known as coeliac disease).
If you have a food allergy, you may have symptoms that include:
·itchy or swollen lips, mouth, tongue and throat
·skin reactions (eg swelling and itching, a rash around your mouth, eczema and flushing)
·wheezing or shortness of breath
·diarrhoea, feeling sick, vomiting and bloating
·coughing
·a runny nose
·sore, red and itchy eyes
These symptoms may be caused by problems other than a food allergy. If you have any of these symptoms, see your doctor for advice.
If you're severely allergic to nuts or peanuts, your allergy may be triggered just by touching or being near someone who is eating them or has done recently. You may also have a reaction as a result of being in the same room where nuts have been. Using cutlery or crockery that has been contaminated with traces of nuts may also cause an allergic reaction.

Some people develop a severe, whole-body allergic reaction called anaphylaxis, or anaphylactic shock; a rare but potentially fatal allergic reaction. Symptoms can include dizziness, a rapid pulse, a rapid drop in blood pressure and swelling of the airways and throat, making it difficult to breathe. If this happens you could lose consciousness if not treated.

Interestingly, the exact reasons why some people are allergic to various foods aren't fully understood.

For some people with a food allergy, sensitivity may develop before birth while they are in their mother's womb (uterus). It's also possible that this may happen as a result of breastfeeding (although this isn't the case for peanuts). Ask your doctor or your midwife or health visitor for information.
If you have other allergies or conditions such as eczema or asthma, you may be more likely to develop a food allergy. If someone else in your family has these conditions, this can also increase your risk of having an allergy, although it may not be to the same thing.

There is some evidence that some babies may become sensitised to nuts as a result of being treated with skin treatments for eczema or other allergic conditions that contain peanut oil, or from peanut oil found in certain sorts of formula milk and nipple creams.

Yes I went through this with my youngest. When you go to see the doctor he will most likely ask about your symptoms and examine you. He or she may also ask you about your medical history.

If an allergy seems likely, your GP may refer you to a specialist allergy clinic for tests that may include:

Skin prick tests - an extract of the suspect food is put on a small patch of skin, usually on your forearm or back, and a very small, fine scratch is made. If redness and swelling develops around the scratch, the test is positive for that food.

Elimination and challenge diets - where you remove the suspected allergy food from your diet and replace it with another food. If your symptoms improve, a diagnosis can usually be made. To confirm this diagnosis, your doctor may ask you to re-introduce the food back into your diet. If you have had severe allergy symptoms in the past, this will be done under medical supervision in hospital.

Blood tests - these are useful if you have a severe food allergy and are at risk of anaphylaxis from the tests above or if you have extensive eczema or dermatitis and can't have a skin test. The RAST (radioallergeosorbent) test measures levels of food-specific antibodies in your blood.