I have been getting hives that go away when I sleep and come back during the day, what could they be?

For how long? Hives present <6 weeks are often due to food or drug allergy. Could be any food but dairy, egg, wheat, soy, corn, seafood, peanut, sesame & tree nuts are most common triggers. Antibiotics, Aspirin & Ibuprofen are common drug triggers of hives. Herbal remedies & supplements & viral infections are other causes. Daytime only symptoms suggests something you are swallowing but that's not absolute.