Equalizing your ears is difficult and dangerous when you have a head cold. In addition to congesting your Eustachian tubes, the mucous and bacteria in your airways can be forced into your middle ears when you equalize. This can cause an ear infection, so avoid diving when you have a cold.

You should avoid using decongestant medications when diving. These drugs can wear off while underwater and cause a condition known as a reverse block, which is covered later in this lesson. Additionally, the increase in pressure can intensify the adverse effects of these medications and cause extreme drowsiness or other complications.

Swimmers often use earplugs to prevent ear infection when swimming, but they are not safe for diving. Earplugs create an additional air space outside of the eardrum that cannot be equalized.