4yo son’s mysterious rash

Charlotte-Louise

I noticed last Friday (9 days) my son has had a rash developing on his underarm(only one side) though initially it was just eczema or psoriasis as both him and I get the odd patch of psoriasis pop up every now and then, but this rash carries on getting worse so I took him a pharmacist, he had no clue what it was but said it’s not eczema or psoriasis, took him to a second pharmacist and she didn’t have a clue either but again said it’s not psoriasis or eczema or viral or bacterial or fungal. So I took him to the doctors, even he didn’t know what it was. All 3 of them told me to give him antihistamine suspension and apply a steroid/ antihistamine cream which I have been doing but the rash hasn’t gotten any better, it’s showing no signs of slowing down, I have been dressing his in loose cotton tops and he’s been going to bed unclothed on his top half, keeping the area clean but not sterile as I don’t want to do any more damage by applying harsh chemicals or stripping away his body’s natural barriers, I ha ent ch ages my washing powder or anything like that, I’ve been racking my brain trying to think of anything that could of irritated his skin but I can’t think of anything, it’s harder when not even a gp can give you a hint as to what it might be 😑 I’ll put pictures below starting from friday. If anyone else’s child has had this or if it looks similar to something you e had before please comment with your theories 🙏🏼 the doctor didn’t seem too worried about it so I’m not super worried, it’s just frustrating not knowing what it is and if there’s potentially anything else I could be doing to help. He says it’s itchy although I don’t ever see him it itching it, sometimes he says it’s dinging which I think means tingling 🤷🏼‍♀️

Any info greatly appreciated 😇