I have a single itchy bump on my arm that looks like a bug bite. it's winter though. what can it be? no bed bugs, fleas, etc. in home...

? Fungal or bug bite: Sometimes a fungal infection or "ringworm" will start as a slightly itchy red bump that then enlarges in a circle form. More likely, with all of the fresh evergreens with the holidays, you may have picked up a chigger or other biting insect. Fleas have also been known to hitch a ride. I have occasionally had fleas hop off patients in my office, and they do jump!