Hi Betty
It's true that Cairo can be rather smoggy at that time of year so if you have serious respiration issues you should have a word with your doctor, and make sure you take any inhalers that you use.
However, you won't be exposed to the smog for very long as you will only be in Cairo for two nights - most of your holiday will be spent on the Nile, away from the capital.
Kind regards,
Olly, your editor