If you develop symptoms of a food allergy, your doctor will have you undergo a skin test or blood test to determine which foods you are allergic to.
Food allergies occur when your immune system treats normally harmless food as a dangerous bacteria, virus or another infectious agent. Symptoms of a food allergy range from mild, such as rashes, to serve, in the case of anaphylactic shock. These allergies are more common in children than adults.
Testing for food allergies involves undergoing a skin test or blood test.
- Skin test (called skin prick test): This involves placing small amounts of one or more of the suspected foods on the skin and pricking it with the needle. This allows the food particle to get under the skin. If you develop itching or a bump within 15 to 20 minutes, you are probably allergic to that food.
- Blood test: This involves removing a small amount of blood from the vein of your forearm and testing it for Immunoglobulin E (IgE) antibodies after ingestion of certain foods. IgE antibodies are substances that are produced in response to ingestion of the food that you are allergic to.
Sometimes, your doctor may recommend you to undergo further testing, such as:
- Oral food challenge test: This involves eating or drinking small portions of food in increasing amounts over time to watch for any allergic reaction. This test is usually done under a doctor’s supervision at their office or in a hospital.
- Elimination diet: This involves removing all suspected foods from the diet and then adding them one by one to find out if any one of them is causing the allergy.
What are the most common food allergies?
Testing for food allergies will let your doctor know if your skin problems, such as itching and bumps, are due to any food allergy or a skin condition. It may also be used to find if you have a true allergy or sensitivity to the food.
The most common foods that cause food allergies include:
- Milk
- Soy
- Wheat
- Eggs
- Tree nuts
- Almonds
- Walnuts
- Pecans
- Cashews
- Peanuts
- Fish
- Shellfish
Food sensitivity (also called food tolerance) will usually result in digestive problems, such as abdominal pain, cramps, nausea, vomiting or diarrhea. The common ingredients that result in food sensitivity include lactose (found in dairy products), gluten (found in wheat) and monosodium glutamate or MSG (found in many foods).
When will you need testing for food allergies?
Your doctor will ask you to undergo testing for food allergies after taking your medical history, looking for signs and symptoms and performing a physical examination.
They will ask you questions, such as:
- Whether you have a family history of food allergies
- Whether you have hay fever or eczema
- Whether you suffer from asthma
Signs and symptoms of food allergies include:
- Hives
- Tingling of the skin
- Itching of the skin
- Red itchy eyes
- Redness of the skin
- Abdominal pain
- Metallic taste in the mouth
- Swelling or itching of the tongue
- Coughing
- Nasal congestion
- Wheezing
When to seek urgent medical help
If you develop anaphylactic shock after ingesting suspected foods that cause allergies, you need to call 911 immediately. Signs and symptoms of anaphylactic shock include:
