It could be due to an allergy to whatever fabric detergent and/or softener (dryer sheets) that you're using. I have an area on my right forearm that just feels super-itchy every now and again. I look down (usually before or during scratching) and can see a break-out of little welts.

My skin is super-sensitive. To fabrics, perfumes, dyes & whatever else they use in detergents nowadays. Sticking to the products that are fragrance and dye free work a lot better on me! Perhaps you should give that a try & see how those bites do then???

Best wishes to you!