Reaccuring knots on forehead. They appear then go down after a few hours. Went to two dr. S and they have no idea what it is. They are annoying me?

Hives? Temporary swelling which resolves on a few hours is consistent with hives. Are there any other symptoms sich as joint pains? Antihisitamines such as zyrtec (cetirizine) could help. If persists blood tests should be ordered.