Is there anyone medical that can give me advice please?

I am covered from my ears to my feet with itchy welts. It goes off when I have antihistamine and drink lots of hot water, but i soon as I eat anything it all comes back. Some of the rashes look about an inch big, my skin is red hot and I feel chilly.
I have hypoparathyroidism, could calcium suppliments be causing this or do you think it is something else?
Thank you for any advice

Sounds like something you are ingesting. I would suggest going to the doc and having them check you out. It may be the only way you are going to find any relief. I am not familiar with hypoarathyroidism. So, it may be possible that the condition is contributing to your demise. Also, supplements have other ingredients added to them. It may be that one of the additives in the supplements could be causing the reaction. Consult with you physician.

You could be allergic to food products such as peanuts,exotic fruits or something you have always love to eat on a daily basis or seasonal items on the shelf at the grocery store.
Weed it out and separate the consumed foods and write it down on a note book to keep track.
Preservatives in some processed foods can give you the hives. Are you allergic to seafood such as shrimp,shells,clams,fish products.
Be very cautious if it happens again. See an allergist.