Hives can recur because the clinical manifestations of hives are itchy skin and recurrent skin bumps. The flakes may subside on their own within a day and leave no trace, but this does not mean that the hives get better and they can recur. If the hives are cured after medication, the rash will not recur. Hives that heal in a short period of time are called acute urticaria, but if they recur more than twice a week for more than six weeks, they are called chronic urticaria. Some hives are due to food allergies, such as fish, shrimp and crab, or allergies to food additives, colors, condiments, preservatives, etc. Some hives are allergic to pollen, dust mites, animal dander, feathers, formaldehyde, etc. In addition, some medications can also induce hives, as well as bacterial, viral, and parasitic infections, which can also trigger chronic recurring episodes of hives. Various chronic diseases, including chronic gastritis, enteritis, and thyroid disease, as well as insect bites and neuropsychiatric factors, can also cause recurrent episodes of urticaria.