Is BMI same as percentile for children?

[Lowren]

2 year 4 month old DS has non igE cow milk and soya allergies. I am growing increasingly concerned that he's allergic or intolerant to something else, as he's having symptoms of a reaction intermittently and despite food diaries I cannot figure out what it is.

HV said that she's not worried because his BMI is fine. I've just looked in the red book and I cannot decode the height and weight numbers but for BMI she's written 15.8. She has not plotted it on the graph.

I am trying to look online how far into the healthy range that is, but everything I can find says that BMI in children is given as a percentile.

If the 15.8 is the percentile, is the case, I am surprised she immediately dismissed it as fine. When he was first ill with allergies as a baby, he dropped from the 50th percentile to the 9th.

After diagnosis he dramatically improved and climbed to the 75th where he stayed for quite some time. He's always been very tall and when he was doing well, he had a good appetite and started looking a lot more in proportion with his height.

If the 15.8 is the number as a percentile, then I feel that is a significant drop following the intermittent return of the symptoms, especially because he has been ill again following the weighing and even family members have noticed he looks slimmer. I want to be sure I'm not mistaken about what the BMI number means before getting back in touch, as I do feel I've been labelled a bit of a paranoid mother.

Battling to get him diagnosed as a baby was really stressful and seeing him get better and thrive the way he was "supposed" to for all those months was heartbreaking. I am confused why it seems to be getting worse now and I don't want the same to happen again where we are fobbed off repeatedly.

Do you know his height and weight?
If so, put his details in here: https://www.nhs.uk/health-assessment-tools/calculate-your-body-mass-index/calculate-bmi-for-children-teenagers

And it will calculate his centile, and tell you if it's healthy or not.

I don't as she's written it but I can't read what it says. I will weigh him tomorrow and see if I can get him to stand still enough to do his height too, I was hoping to use hers as I guessed they would be more accurate but I'll check it myself tomorrow to make sure. Thank you.

My children changed centiles quite dramatically but all was fine.
Allergic symptoms usually involve a rash/swelling, does your child have anything similar?
Could it be an autoimmune disorder such as Coeliac disease (which is neither an allergy or an intolerance)?
https://www.coeliac.org.uk/information-and-support/coeliac-disease/about-coeliac-disease/coeliac-disease-in-children/

Thank you. He gets itchy all over when this happens, and gets patches of dry and red skin quite frequently, but he's never had many skin symptoms with his allergies and doesn't get swelling. He has non IgE allergies and most of his symptoms are digestive in nature.

https://www.allergyuk.org/resources/does-my-child-have-a-cows-milk-allergy/#:~:text=Delayed%20Symptoms%20(Non%20IgE%20mediated)

DH is suspected celiac but has not been diagnosed. He gave up gluten as a teenager and cannot reintroduce it into his diet to test as even a crumb of contamination with gluten makes him very unwell for days and days.

So that is a concern for DS, but the one time I mentioned this to GP he said they only test children if they stop growing/putting on weight. So it's another reason I want to make sure I keep an eye on it if it's dropped. Thank you.

Normal BMi for children is 5th to 85th centile. Its a massive range.

Thanks for replying. I know it can be normal to be on any of those centiles but I thought that dropping from a higher to a lower would be concerning. It sounds like it’s not necessarily a problem though. I’ll measure and weigh him to check today and then just keep an eye on how he goes.

Do you have any previous measurements to compare the BMI too?
You are right they shouldn't just be looking at the absolute value but also whether it's changed over time. A child that has always been on the 15th percentile for BMI is different to one that 6 months ago was on the 50th percentile.
I'd probably ask for a dietician referral to try to help identify other allergies. I'd keep a detailed food diary too, to help with identification. My daughter has 20 nonige allergies and this was the only way we could get to the bottom of things. The itching possibly would suggest ige allergy instead in which case skin pricks or blood tests might help identify it. I'd probably say start my checking eggs, gluten and nuts as the next most common allergens but they can be allergic to anything, my daughter is allergic to more vegetables than top14 allergens!
It might not be food, if you are struggling to identify patterns it could be something like house dust mites or hayfever

When you mean you can't decode the height and weight from the red book what do you mean?

At that age, a BMI of 15.8 is on the 50th centile. Layout 1