Opinions please on whether this is heat rash or contact dermatitis ? It’s been absolutely roasting last couple of days having been keeping my 9 month old cool as I can but this rash appeared on tummy now one day later it’s spread over whole stomach. No other symptoms in good mood and eating well no temp. But also to note my MIL brought a different washing liquid over we usually use fairy sensitive only in the wash as he is prone to eczema.