If your child has eczema and has been avoiding a food that he/she has been tested positive in the Skin Prick Test (SPT), it may be time to review if there is indeed a true food allergy. Research indicates, as I understand from various online articles, that the skin prick test is a test of sensitization, and not clinical relevance. Below are some points on the accuracy of skin prick test:
1. Skin Prick Test is more accurate for non-food allergen, such as dust mite and pollen, than for food allergen.
2. Skin Prick Test is More Accurate in predicting when there is NO food allergy and Less Accurate in predicting a Positive food allergy. The implication of this is that children who have been avoiding food (for example more than 50% of those tested positive for milk and eggs, and more than 70% of those tested positive for peanuts) actually didn’t have an allergic reaction to these foods. (There is only a 0.5-10% chance that a child who is allergic to a food will test negative for it.)
3. Follow-up tests are required for skin prick test for children at different age, sometimes about 1-2 years later. The results can be different as children may ‘outgrow’ some allergy or develop new ones? (hopefully not…)
4. An oral food challenge is the most accurate (less than 5% incorrect).
5. For children with eczema, there is an 80% possibility that food that the child is avoiding turn out not to be one he/she is allergic to. Refer to this article for detailed research.
Despite above, Skin Prick Test still remains the most recommended first test for allergy, as it is by comparison simpler, lower cost, faster results, more tolerated (children won’t feel much pain, you can read this post on my baby Marcie’s experience) and more accurate than blood test. If anyone has an experience to share on skin prick test for your child, do comment below this post.