Just wanted to point out Piriton tablets contain lactose so not recommended for those with severe milk allergy due to possible contamination with milk proteins. We were also told that tablets don't work as quickly as liquid but maybe this is incorrect? However during a reaction when throat gets itchy I think liquid would probably be better. You can take full size bottle in hand luggage as long as it has prescription label or you have copy of prescription otherwise has to be 100ml max.
Interestingly someone at Anaphylaxis Campaign recently told me that current guidance states that cetirizine should be prescribed not Piriton as it doesn't make them drowsy so it's easier to tell if drowsiness is due to reaction rather than meds. I'm planning to ask consultant about this at next appointment.