This.
When DC2 was 18 months old, he had a day of being really cranky and had a temperature; the next day he had spots around his mouth, on his arms, hands, legs and feet. Temperature was gone and was pretty much okay in himself.
Took him to GP (called beforehand so could be seen in isolation) and she diagnosed him with chickenpox and impetigo 🤨 I was a bit suspicious as was originally thinking it was hand, foot and mouth and he had maybe one spot on his back but believed the GP.
Funnily enough the spots didn't really bother him and DC1 didn't catch it from him...
Fast forward 2.5 years and chickenpox is going around DC1's class... DC1 inevitably catches it, completely different presentation to DC2, but overall not too bad, a bit itchy but not masses of spots.
A bit blase as DC2 had "already had them", kept sharing baths, saliva, towels, generally as close and gross as two siblings could be. Fast-forward again two weeks and DC2 is absolutely covered in spots, so miserable and misses his birthday party 😔
Looking back at photos and with hindsight thinking back to symptoms, it was totally obvious (except to the GP 🤨) that he had hand, foot and mouth previously. Obviously there's not much I could have done to prevent it, but the severity of chickenpox is all about viral load, so I probably would have been a bit more cautious with how they mixed, made them have separate baths, towels etc.