Sore mouth in a 5yr old

[theimpster]

My son started complaining of a sore mouth last night, and it is still sore this morning. He doesn't have any visible sores or ulcers and says it is sore all over. He doesn't have any other symptoms, but I did change his toothpaste recently. If he had a reaction to the toothpaste would I be able to see anything? Or does anyone have any ideas what it could be otherwise?
Cheers.

[theimpster]

He's developed a rash all over his torso now. Any idea if they're linked?

[PJ67]

My son sometimes says his mouth is sore and points in it but actually means his throat. Is it possible he has had a sore throat as start of a viral illness? Hope he's better soon.