Hi and welcome to HCM If your child has been on vyvanse for a while now without previous reactions, it is unlikely that an allergy started suddenly. It would have normally shown up in the beginning itself. check for bumps in genital area, armpits, between fingers and toes etc If he was diagnosed with scabies, I would advise another round of treatment , applying permethrin cream all over body overnight (excluding face) and bathing in morning. Clean all clothes an bad linen in hot water and sun dry them. It is always advised that all affected family members be treated at the same time to prevent transmission again. Apply a calamine lotion for itching and antihistamine at night. Also rule out any other allergies like food, dust, pollen, insect bites or any new meds etc Hope this helps you.