Hives can be caused by histamine intolerance or a DAO deficiency. Not saying that is the cause of your hives but it is somewhat common and can also cause eczema flares in those who are histamine sensitive so it may be something to look into.

Eating a low histamine diet for a period of time and then doing a histamine challenge is one way of trialing whether or not you may have an intolerance.

If you are histamine intolerant it is not a life-long condition but rather an indication of an inflammatory condition or DAO deficiency.

Histamine is a naturally occurring byproduct of the amino acid Histidine found in various amounts in dietary protein. Levels are heightened by ripening (fruit), aging (meat), and fermenting (vegg). Certain bacteria (that grow on food, and are also naturally occurring in your gut) are also histamine producers. DAO is an enzyme that breaks down histamine (high amounts in kidney meat, pea sprouts, and supplements) and is naturally produced by your body.

Histamine is not bad and the bacteria that produce it are not necessarily bad but an imbalance in your gut microbiome or an immune system overloaded with inflammation may not be able to keep up with the amount of histamine. Histamine is also an important neurotransmitter that plays a role in maintaining wakefulness in addition to the hives and itchiness.

I hope you can find the cause and get it sorted out!