You can always arrange another. So decrease the amount of caffeine you normally consume on days you are going to fly. Another problem in planes is lack of air circulation. I usually have to take more medication and have to wear a mask. I wouldn't hesitate to ask the flight attendant to move to another seat if you are near someone who is wearing too much fragrance.
Lets talk about how to avoid catching colds on a plane.
The most common way that we transmit the cold virus is on our hands. Mamu I request a change of seat from the steward or stewardess. If they balk, I tell them they really don't want me to have an asthma attack en route. The cold viruses can be airborne as well. So, we all have to make a concerted effort to keep our hands away from our nose, mouth and eyes.