Flying may also aggravate respiratory problems. People like to blame air pollution but the air in commercial airliners is probably the cleanest air you will ever breathe. It is the dry air that can result in coughing, sneezing, bloody nose and other respiratory symptoms. Drinking a lot of fluids may help. It is also a good idea to carry along a decongestant or cough medicine in case the symptoms become intolerable.
Constipation is a consequence of too little activity and too little fluid.
Actually, more international travelers complain of constipation than of diarrhea. Exercising your muscles and drinking plenty of fluid is a good preventative. Then there are cuts, bumps and sprains that are such a common part of life but so much more annoying when away from home. Ice and elevation are the hallmarks of initial treatment. Even a cut that will need stitches will bleed less and swell less if an ice pack is applied while waiting for treatment.