Food allergies and how to spot them

The most common childhood allergies are to eggs, milk, and peanuts. Others include wheat, soy, and tree nuts (almonds, hazelnuts, cashews, and pistachios). Peanuts, tree nuts, fish, and shellfish tend to cause the most severe reactions.

Many children grow out of food allergies by the age of five years. It's not known why food allergies develop, but you're more likely to have a food allergy if you also have hay fever, asthma, and eczema, or if anyone in your family has these. With eczema, the earlier it appears and the worse it is, the more likely a food allergy will emerge.

Shellfish tops the list of food allergies in adults. Childhood allergies more likely to persist include peanuts, tree nuts, fish, and shellfish. Some fresh fruits can also cause a reaction. If you have a true allergy, you only need a small amount to provoke a response, and reactions can get worse with repeated exposure.

The most accurate way to work out if you or your child has an allergy is to keep a food diary. List the foods you've eaten, any symptoms, and how long after eating the symptoms came on. This will help you spot any patterns and pinpoint potential allergies.

Gut symptoms may give you stomach pain, nausea and vomiting, and diarrhea. You may notice a red, raised itchy rash, known as hives (urticaria), or your eczema may get worse. You may get itching or tingling around your mouth and throat, and perhaps mild lip or tongue swelling. This happens particularly in allergy to certain fresh fruit and vegetables and is avoided by thoroughly cooking them.

Mouth and throat symptoms carry a risk of the airways swelling and causing breathing problems. This is potentially life-threatening and can lead to a condition called anaphylaxis, where you are unable to breathe. This is a medical emergency and requires immediate medical attention.

Any food allergy symptoms can come on within seconds or minutes of eating – this is usually an immunoglobulin E (IgE-mediated) allergy. This carries the risk of breathing problems and anaphylaxis. Alternatively, a non-IgE-mediated food allergy may take several hours to come on, so is harder to pair with a particular food. It's caused by other parts of the immune system.

A food intolerance is not an immune reaction, so it's not a true allergy. It's a difficulty digesting a particular food. Gut symptoms may be similar to allergy, but with more bloating and excess gas. The most common food intolerances are to lactose and casein, both found in milk, and to gluten in wheat and some grains. Gluten intolerance is separate from celiac disease and wheat allergy.

The best way to prevent an allergic reaction is to avoid the offending food, so it's important to identify it. If you have suspicions for yourself or your child, book an appointment with your doctor, who will listen to your concerns, look at any related medical conditions, and they may refer you or your child to an allergy service. Take your food diary to any appointments, as this will help with assessing you, and they may consider allergy tests.

If your asthma has flared up and you think this may be related to a particular food, again, book an appointment with your doctor to discuss the next step in treatment or referral.

Although rare, food allergies can be life-threatening if anaphylaxis occurs. It is not common, but it is life-threatening and can develop quickly. It causes swelling of the airways and difficulty breathing, along with feeling faint, dizzy, and sick, and you may collapse. Someone should call 911 immediately with any of these symptoms.

If you've had an anaphylactic reaction, you may be prescribed an EpiPen, which you will carry at all times. This contains epinephrine, and you will be taught to administer it in the event of an emergency. It's a good idea to wear a medical bracelet, too, to alert everyone in the event of an emergency.