I Woke Up With What Looked Like A Sunburn On

I woke up with what looked like a sunburn on my lower neck into the chest, it doesn't itch but is hot to touch. As the day went on it has now spread to the sides of my neck in line with my ears. I do not have allergies to food, drugs and considered healthy for 52. I've been on estrogen replacement since 31 from hysterectomy with bilateral oophorectomy.