Why do planes mess me up so bad?
 

On my last few flights, I’ve come off my airplane feeling incredibly sick (sore throat, headache, etc) despite feeling completely fine 7 hours before at the departing airport.

This has happened 3 times now, once a year ago on my last vacation to Wales,a few weeks ago when I went to France, and today, the day I got back from France.

Is there a reason why planes make me so sick?

The cabin crew frequently complain of similar symptoms when we are operating Chemtrail flights. Its a well known side effect.

Must be the air conditioning; I often feel very dry even after a shortish flight but a couple of those little bottles containing amber coloured liquid with a couple of ice cubes from the bar usually cures it unless it's Ryanair who serve you plastic sachets instead of bottles.

From your location and destinations, you appear to have been crossing the Atlantic. If so, could be related to time zone changes.

Air travel messes with your body. Stress just getting to the airport and once there you have to deal with being treated like scum by the staff. In the air your life is in the hands of whoever would do the job cheapest. In the cabin you're in a small space where you can't move, and so the lymphatic system (which is pumped by muscle movement) doesn't work properly. All the little pressure vessels in your body expand and press on other bits of your anatomy, in the skull that causes headaches. You're in close proximity to eight other people who are all shedding their diseases onto you.

No wonder you feel awful.

Aisle seats and lots of fluids is my unscientific recommendation. More space, better air circulation and easier to move about. Or just avoid non-solo flying whenever possible.