Why Does Pressure Buildup in the Ears Occur?

One of the most important parts of the ear is the Eustachian Tube. This small passage connects your middle ear and your throat and serves to equalize the two. This prevents the buildup of fluid and air pressure in the ear.

Where things go wrong is when the Eustachian tube gets clogged. Because there's no longer an equalization mechanism, this causes pressure to start building up, leading to discomfort or even pain. As to what you can do about it, that depends on what's causing the blockage.
Woman getting hearing exam from audiologist to check ear pressure

What Are the Causes of Pressure Buildup in the Ear?

Sinus Issues
If your sinuses are congested due to allergies, viral infections, a sinus infection, environmental irritants, or the overuse of tobacco products, this can create an unpleasant feeling of 'fullness' in the ear. In order to treat this, there are several steps you can take. First, if possible, avoid whatever caused the irritation.

Beyond that, you might consider using a nasal decongestant or saline irrigation solution. You may also consider investing in a humidifier or pursuing aromatherapy. Steam inhalation can also help, and drinking plenty of fluids is always advisable, whether or not you are ill.
Fluid Buildup
Similar to how congestion in the sinuses can cause pressure buildup, fluid buildup in the ears can be caused by colds, sinus infections, allergies, or barotrauma. This most commonly manifests as popping or ringing, hearing loss, dizziness, and balance issues. As you might expect, this is somewhat more severe than simple sinus issues, as it can cause the sinus to rupture if left untreated. 

To remove the fluid, try tilting your head towards your shoulder and tugging on your earlobe. If this doesn't work, apply a hot compress for 30 seconds, remove for one minute, then repeat. Finally, try an over-the-counter ear drop. 

And if none of these remedies work, we'd advise visiting a doctor.
Excessive Earwax
Earwax buildup, known also as cerumen impaction, is most often caused by overusing cotton swabs or other objects in earwax cleaning. It's also linked to overuse of hearing aids, earplugs, or earbuds, as well as swimming and certain genetic conditions and illnesses.

The safest and most effective way to treat this condition is by visiting an ear, nose, and throat specialist, though it can be treated at home with a saline solution or cerumen softening solution.
Since allergic reactions can cause similar conditions to sinus infections, it follows that they can also result in pressure buildup in the ears. Fortunately, treatment is extremely simple. Just take antihistamines and decongestants. 

Do note, however, that some tend to have side effects such as severe drowsiness.
Airline travel
The rapid change in air pressure during takeoff and landing can cause a great deal of discomfort and pain. In order to counteract this, try chewing gum, yawning, or swallowing. You can also try closing your mouth, pinching your nose, and blowing it gently, or using filtered earplugs. Finally, you can try using a nasal spray about 30 minutes to one hour prior to takeoff and landing.
Ear infection
An ear infection can occur in either the middle ear or the outer ear. Though the causes and symptoms vary, they usually tend to resolve on their own, though ear drops and pain medication may be beneficial in helping you deal with the symptoms. If, after a few days, your ear infection either doesn't improve or continues to worsen, visit your doctor.

No Pressure

There isn't a single cause of pressure buildup in the ear. But by understanding the various issues that can cause it, you can better understand how to deal with it. More often than not, home treatment will be enough — though that said, a doctor's visit is a good idea if the symptoms last longer than two weeks or worsen over time.