How to clean your iPhone
Clean your iPhone immediately if it comes in contact with anything that may cause stains, or other damage—for example, dirt or sand, ink, makeup, soap, detergent, acids or acidic foods, or lotions etc.
Unplug all cables and turn off your iPhone (press and hold the Sleep/Wake button, and then slide the onscreen slider). Use a soft, lint-free cloth—for example, a lens cloth. Avoid getting moisture in openings. Don’t use compressed air.
Your iPhonehas a fingerprint-resistant oleophobic—oil repellant—coating. This coating wears over time with normal use. Cleaning products and abrasive materials will further diminish the coating and might scratch your iPhone.
Don’t use window cleaners, household cleaners, compressed air, aerosol sprays, solvents, ammonia, or abrasives to clean your iPhone. The front glass surfaces have an oleophobic coating. To remove fingerprints, wipe these surfaces with a soft, lint-free cloth. The ability of this coating to repel oil will diminish over time with normal use, and rubbing the screen with an abrasive material will further diminish its effect and might scratch the glass.
To clean the Home button (allowing Touch ID to work optimally), wipe it with a soft lint-free cloth.
To clean the dirt that might accumulate around the SIM tray opening, use a soft lint-free cloth and place a very small amount of rubbing alcohol on it. Very gently wipe the dirt away from the port opening and avoid getting any of the moisture in the opening.
Keeping your iPhone clean will optimize the performance and it looks better too.