Rash in a 2 year old

[NAB3]

Just taken DS2's PJ top off and he has a rash on him. Behind his neck and the top half of his torso. Just given him a small dose of Piriton but does it sound like anything anyone recognises please? TIA.

does he have a fever?
my DS often gets a rash when he is hot, or when he has a virus

Any other symptoms?

has he been ill recently? Sometimes a rash shows up after a viral illness.

Are they new pjs?

Hi
What a morning! A mum at school thought it looked measlesy so off I went to the pharmacist to check. She didn't hink it was but I went to clinic to get the HV to look. It isn't measles but she wasn't sure. I will keep an eye on him. Thanks all.

It gets better. This mornings rash has pretty much gone then this afternoon he has bright red rashes all over his back and top of his bottom. A different pharmacist looked at him and thinks it may be an allergy. Just been and got some Fairy detergent and debating whether to rewash all his clothes in case it was the detergent.