What Causes Recurring Itchy Hives On The Neck?

The past 9 months I have been getting what I call hives on my neck in my hairline area. I don t get them every day and when I do I ve been doing something different or I ve ate different things. I don t know what is causing this reaction. They don t hurt but are very itchy and are only on that area first then can spread to other places on my body.