Hello. Welcome to ask the doctor.
I understand your concern.
As per details, there are following possibilities for such rash,
1) Lichen planus- it is characterised by violaceous flat-topped papules over body. These are itchy and have tendency to form new lesion on scratching leading to formation of linear rash. The rash develops over a period of time
2) Insect bite- usually has linear red rash in the direction of movement of insect. It is noticed all of a sudden.
Treatment depends on the diagnosis.
I will advise you to visit your doctor so that he can do physical examination of your child and give you prescription.
You can share my opinion with him.
I hope it helps.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.