Many thanks for that.
The reaction lasted about an hour of feeling ugh; runny nose and slightly laboured breathing (but then they were rushing to catch a plane - hence the urgency of the question)
He was then OK. I think he metabolised the aspirin quickly and then all was well. Not sure if they took the Piriton, as their phone was off during the flight - will let you know. It's always good to get feedback to expand understanding of individual cases - I hope you agree.