How can I tell if it's roseola, chicken pox or something else? He has had all his vaccinations.

Hello,

In order to answer properly, I need to validate some elements

How long between the onset of the fever and the appearance of the first lesions?

Are there any red patches through it?

Did he have any other symptoms?

It sounds like roseola. I can't say beyond a shadow of a doubt that this is what it is since I can't see it, but based on the symptomatology you describe, it is very likely

Roseola is characterized by a fever above 39 degrees that lasts 48-72 hours. This is the period when the child is contagious. When the fever subsides, often within 24 hours, skin lesions can be seen. These lesions are harmless and are usually located on the chest and neck (more rarely on the arms and legs). There is nothing to do except moisturize the skin as needed. The child is no longer contagious after the fever has broken. The rash should go away on its own within a few days. Since there is no vaccine against roseola, it is much more common in children than measles, rubella or chickenpox, diseases that can easily be prevented by vaccination. However, if your child develops other symptoms or if his general state of health deteriorates, I suggest that you talk to a doctor

It's a pleasure!