What causes tinnitus?

Answer
Tinnitus can be caused by a variety of factors, some of them not under your control, such as simply aging. Most often, tinnitus is caused by repeated exposure to excessive loud noise. 

The good news is, tinnitus is not a sign of a serious medical problem, and it can be managed.

The most common tinnitus triggers are:
Loud sound. Whether it’s a great concert or a plane taking off, exposure to loud noise can damage your hearing.
Stress. Stress from difficult life circumstances can affect your entire body, including your hearing.
Alcohol. Excessive use of alcohol and quinine water, found in the ‘tonic’ used in many mixed drinks, can trigger tinnitus.
Smoking. Smoking narrows the blood vessels that bring oxygen to the sensory cells of your ears. 
Medication. High doses of aspirin and NSID pain relievers are a known trigger for tinnitus, as are some antibiotics and anti-depressants.
Salt. Too much salt can cause tinnitus
High blood pressure can increase tinnitus symptoms, so sufferers should cut down on salt. 
Caffeine. Coffee, dark tea, cola, and energy drinks all contain caffeine, and some sufferers say eliminating them helps control tinnitus.