Thyroid UK
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Is the lactose in my thyroxine causing baby's allergy?

I have a dairy allergic 8 week old baby, who i am breastfeeding. Could the lactose in my thyroxine be making him ill still (he's 80% better since i eliminated all dairy and beef from my diet) or is he probably allergic to something else too? I've talked to my GP about getting the lactose free thyroxine but the health board are reluctant because until he's 1 a blood test won't firmly confirm his allergy.

7 Replies

If I were you I would ask to see an endo or pediatrician- they are more likely to give you (and your baby) purified T4 as having to cope with this problem for months would cause you and baby significant stress.

Moggie x


I thought that dairy allergy or intolerance is caused by the proteins in the milk rather than the milk sugar, lactose.

Lactose intolerance is when a person lacks the enzyme to break down the lactose - my unerstanding is that, unlike a food allergy, this doesn't involve the immune response and therefore doesn't come with the danger of anaphylatic shock.

Also, I think that the main carbohydrate in human breast milk is lactose. Babies should have more of the lactase enzyme than adults because their main food is meant to be milk! He will still be getting lactose from your breast milk, probably in much greater quantities than from your medication.

However, I do not know if there is a difference between the lactose in breast milk and that in medications. I don't think there is, but if you're still worried, then I would play it safe.

Do you eat wheat? That's probably a more allergenic food than even milk.


No, i'm not worried about the lactose per se, it's that there is still a small amount of cows milk protein (that's what he's reacting to, not the lactose, though you're right, cow lactose and human lactose are different and human babies have lots of lactase to digest human lactose) remains in even medical grade lactose. But it is a really tiny amount. I do eat wheat, i'm currently eliminating soya, if that makes no difference i'll eliminate wheat but it takes 3 weeks to see if elimination of a given thing helps or not.... And you're also right re: allergy - he doesn't wheeze but he does get a rash so it's hard to know if he's allergic or intolerant to dairy given his main symptoms are vomiting and diarrhoea.


Poor little thing! My eldest used to projectile poo when he was tiny, his poor tummy was in such a state. I wasn't anywhere near as clued up about foods as I am now. I wish I'd known more back then.

Gluten is supposed to increase intestinal permeability even in people without coeliac disease, and I believe that's what allows the partically digested proteins to get through teh gut wall and cause an immune response. If it was me I would give some serious consideration to gluten - you cut out the potential allergen and could be helping to reduce the mechanism that aggravates the problem.

Or it could be the fillers in the tablets at fault!

Whatever it is, I hope you get to the bottom of things.


I don't think that we can possibly do much better than make educated guesses. I think I would include the medical establishment in that as well. They really cannot know even if they try doing a lot of (expensive) investigation.

As far as I am concerned, the health board should pay for at least one lot as trying it is surely the only rational way of finding out? Rather than possibly causing a poor mite to continue suffering, that is what I think they should do. And, whilst disproportionately expensive, it is really not in the "very, very expensive" category.

All the best



Well, thanks for all your advice!

The GP called this morning. He doesn't think the amount of cows milk protein in medical grade lactose could be causing the problem but he understands my concern so he's given me 3 months worth of the lactose free version in order to let me see for myself and so that during eliminations of other foods i can KNOW it's not the medication. He's the best GP in the world!


I know this is an old thread, but can you please let me know if it turned out to be the Synthroid as the culprit? I suspect the same with my little one...


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