If your sister doesn't have bumps, it is probably an allergy or dye reaction. To be on the safe side, you can check your mattress very carefully, if you see any bugs, you can kill them I hear by covering your mattress with a mattress cover and your pillows also with covers. You recently dyed your hair; did you wear rubber gloves when you did this? It's possible that some dye got on your skin and burned a little before you washed it off and may have gotten a little on your hands. It may take a few days to go away.
Also, since the bumps are so few and are not on your legs, stomach or chest area, your bumps and irritation may be as a result of your dye which you must time your application according to instructions and then rinse out thoroughly. If any gets on your skin, neck or hands, must wash it off these areas immediately (or it will irritate and/or rash). If rash or redness occurs again and you haven't used dye, then I would start looking for allergy possibilities and act accordingly, such as switching to unscented soaps and detergents and keeping a list of certain foods (such as shell fish, honey, peanut butter, wheat products, oats, bran, whole milk) if certain foods aggravate it and avoid them for a while. Also avoid wearing flannel and some lotions or overheating can cause irritations and rashes also.