'Never travel without carrying your regular medication in your hand luggage. Keep items such as inhalers close at hand.
A long-haul flight may involve crossing a number of time zones. It can get confusing as to when to take regular medications. If the flight is eight hours or less, it is best to stick to "home time".
Those with diabetes should take their insulin according to the time zone from which they have flown.
It is better to have sugar levels a little higher than normal very low blood sugar levels).
There is a theoretical risk to health from radiation, although in practice it is probably only air crew who need to be concerned. Last year, the EU directed airlines to assess and monitor their staff's exposure to cosmic radiation. A German study is currently looking at cancer among flight crews - there has been speculation that it will show higher than normal levels of breast and skin cancer among female flight attendants.
Flying for long periods in the confined space of an aircraft cabin carries a theoretical risk of contracting respiratory infection from another passenger sitting close by; some people now use specially designed respiratory face masks (available from the Aviation Health Institute, tel: 0044-1-235-202708).
A recent holiday highlighted a minor, albeit painful, condition associated with flight. Three of us experienced considerable ear pain during a descent into Heathrow, despite liberal use of chewing gum, swallowing, and simulated yawning. Readers of The Irish Times have reported that a product called EarPlanes (available from Boots) helps to reduce ear pain during take-off and landing. The specially designed ear-plugs equalise the air pressure on each side of the eardrum and are especially helpful to those with colds, allergies or sinus problems.