Is it bad if a mosquito bite turns purple?

Possibly: It is hard to tell without more information. How long has it been since you were bitten? Is the bump warm and painful? You could either be having a reaction or a skin infection caused by the break in the skin from the bite. Please see your primary care provider.

Normal: Mosquitoes have an anticoagulant in their saliva, so bruising is common. Get help if there are signs of infection. Signs of infection can include: increased swelling, redness, tenderness, ^ pain, warmth, red streaks, purulent drainage, swollen lymph nodes or fever.