Rash on lower back

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Does anyone have any thoughts on this rash on my 10 month old?

Pharmacist recommended we see the GP as they thought it might need antibiotics.

GP thought it was eczema and has prescribed hydrocortisol 1%.

Am not sure about GPs diagnosis as we have just returned from holiday in a hot country. On the last day DD spent quite a lot of time in a car seat and a warm plane, then when I changed her nappy after landing I noticed a bit of an imprint from the nappy on her back, and it was slightly red. I folded the nappy down overnight and it got better, then became more irritated in the morning when she scratched it whilst my partner was changing her.

My instinct is that it’s heat related - was wondering if anyone else has experienced anything similar?

I can see a sort of white line that looks like hives, or is it where she scratched it ?
It needs fresh air, so fold the nappy down, and try not to put her in the sweaty pram/car seat.
Id be tempted to try an antihistamine cream .

Could you try a different nappy brand to see if that helps ?

Thanks for your responses.

Yes the welts are where she scratched it.

Had the nappy folded down overnight, with a tissue tucked down the back, and the lower back looks slightly better, but she now looks irritated where the nappy was folded down, poor thing. She keeps trying to scratch too.

Will go and get some different nappies this morning.