Can I have a post please.. My sons has this on his arm since Sunday I took him to the docs yesterday & the nurse said he’s has an allergic reaction to something & just to keep an eye on it.. But today they seem a lot worse & are starting to blister he has it on both arms I’m going to try get him in docs today but have to wait till 3 to ring for an appointment.. Does anyone know what it could be? Worried mum alert!!!