Hi and welcome to HCM. Thank you for your query.
It can be caused by bites or it can be some infectious disease like herpes
, bacterial infections or allergies. YOu can try to find some protective antiinsect creams. You just must not scratch it and should keep this clean and dry. If you notice pus secretion, redness
spreading or leg swelling you should visit doctor.
Wish you good health. Regards