Itching in both ears is different than itching in just one ear. It is obvious that infection would be more likely to affect only one ear at a time. If you have itching and redness of just one ear, that could be a sign that there is an infection of some sort. If both ears are involved, it is likely due to a common exposure shared by both. Whether that be something as simple as recovering from a sunburn or as complex as some rare rheumatologic condition involving the auricular cartilage is difficult to tell without performing a physical examination and gathering some more information. There are some cases where itching can be a sign of something that is not visible to the naked eye, and these will at times require further testing. For the most part, however, a quick visit to your doctor
is able to diagnose the problem quickly. As you mention, there is cartilage in the outer part of the ear. If this becomes infected, it is difficult to treat this infection fully without strong antibiotics. Please speak with your doctor soon about this.