, also known as urticaria, are skin manifestations of an allergic reaction. They are raised red bumps that are itchy. They occur sometimes when a person is exposed to a substance to which they have an allergy. However, it is important to note that not all red itchy bumps are hives. Similar symptoms can be produced by certain viral infections, by reactions to some medications, by insect bites and through other mechanisms.
The fact that the bumps your having come and go does suggest the possibility of hives. Another way to differentiate hives from other causes of itch are to note whether or not they respond to anti-allergy medications such as Claritin (loratadine), Zyrtec (cetirizine), or Benadryl (diphenhydramine). There are over the counter anti-allergy creams and ointments available as well which can be helpful in differentiating an allergic itch.
Hives are NOT contagious. Generally speaking, to be contagious, a condition must have an infectious component, which hives do not have. As mentioned above, there are some viruses that can cause itchy bumps which are not hives, but these do not appear, disappear, and then reappear. They also usually occur in children. An example is chicken pox. It doesn't sound like you have a virus, though if you are concerned about your recurrent itch, I recommend having a doctor
take a look at it when it again appears.