thanks for posting your query.
The fact that it is getting faded seems to be due to insect bite allergy
this need not be bed bug but can be any type of insect
All you need is to apply simple white vasaline which can soothen the skin.
If the rash
is not better in two weeks you can try mild steroids
like hydrocortisone cream
twice a day for two weeks only
Have a nice day