Hives

My son woke up yesterday with hives, he’ll be 3 in January. So we took him to the doctors cause the hives were spreading we thought it was a bug bite or something else. The doctor said it’s hives and could be a Virus he’s fighting even though he has no other sick symptoms. Any moms have experience with this? Will it ever go away he’s itchy and when he scratches he spreads them. Is it just a Virus or could it be something else? What can I put on the hives?

Thank you!