What is the difference between IgG and IgG4?

If you’re currently looking for a food intolerance test you will have noticed that there are several testing kits available on the market. Before evaluating all the information out there it is important that you understand what the different tests are testing for. Some tests measure all the different types of food specific IgG, like here at YorkTest, while others only measure one of the IgG types.

What is IgG?

Immunoglobulin (IgG) is a type of antibody. Antibodies are major components of the immune system. In normal human blood IgG1 is the most prevalent making up 60-70% of the total IgG, followed by IgG2 (20-30%) and IgG3 (5-8%). IgG4 only consists of 1-4% of the food-specific IgG antibodies present.

Why do some tests only measure IgG4?

There are different types of food-specific IgG antibodies that can be measured; IgG1, IgG2, IgG3 and IgG4. YorkTest measure all four subtypes of food-specific IgG and we therefore describe our IgG testing as food-specific IgG (1-4) testing. We cover all bases to give you your individual food fingerprint. 

igg testing

How accurate is a test for IgG4 only?

There is a complex relationship between the four IgG subtypes. Meaningful results can only be determined by testing for all four subtypes together. 

IgG1, IgG2 and IgG3 are all are capable of causing inflammation which could contribute to symptoms. IgG4 antibodies are only present in low levels and its presence does not relate directly to inflammatory reactions.

Therefore, testing only for IgG4 antibodies in foods severely limits the accuracy of pinpointing those ingredients that are causing significant reactions and could be contributing to your symptoms.

The substantive YorkTest clinical evidence base for food-specific IgG guided elimination diet supports this approach and recognises the fundamental importance of measuring IgG1-4 (total food-specific IgG) and not just IgG4 alone. 

Which test is right for you?

Did you know that the average person who has positive food-specific IgG (1-4) triggers reacts to four to five food and drink ingredients? We have a range of full programmes that could help you uncover what ingredients work for and against your body. Our team of BANT* qualified nutritional therapists can talk through your results and offer advice once you have received your results. If you are unsure what test to take why not test the waters first? Our FirstStep test is a simple positive or negative indicator for a food intolerance.

*British Association for Nutrition and Lifestyle Medicine