Run hot water as hot as you can take it. When its hot enough for you, run the hot water over your bites. Yes it does burn a little, but you’ll feel relief from the hot water drawing the “itch” out. Do this for about 10-15 seconds and then immediately switch to very cold water and run that over it. The shock to your skin from going from hot to cold immediately relieves the itch and it lasts for hours. I can take it pretty hot, so I almost give myself burns, but its worth it.
Encasing mattresses is one of many good parts of a solution, but it doesn't get rid of the infestation. There are going to be other bugs away from the mattress, hiding nearby. What mattress covers are good at is entombing the sometimes large number of bed bugs that can live on a mattress. And because the covers tend to be uniform in color and don't have a lot of seams that the bugs can hide in, it's easier to see the insects.
The size of bed bug bites varies with a number of different factors. Bed bugs inject an anti-coagulant along with their saliva when they pierce the skin to take a blood meal. This anti-coagulant is mostly responsible for how a person reacts to the bite and determines the size of the bug’s bite. Since people will have various sensitivities to the bed bug’s bite, the size of the bite will vary, as well. Another factor that influences the size of a bed bug reaction is the number of times a person is bitten. Bite reactions of people bitten many times are also variable, and their response may be either more or less intense as the number of bites increases.