Taking deep breaths is healthy and can reduce the stress level inside the body, it is automatically
a sign for the brain and body to relax. Actually a natural way of relieving stress
without using other products if it still wouldn't help.
Still we are not much aware of the way we breathe, by taking deep breaths we can be more aware of it because on that moment we focus on this more.

When we take slow breaths the lungs need to work harder for the body, sure there can be something else going on with the lungs when there is a medical issue.
Anyway, when the lungs need to work harder it takes longer for the body to detoxify and to help the heart by pumping healthy blood through the body.
Deep breaths helps also to make the lungs stronger.

When we meditate or do things we become aware of the body like doing sports or going for a walk we know when we need to take a deep breath in and out. Those are the moments to practice it.
When we do this more often aware of it or not we help ourselves and our body, because detoxing is important the longer the toxins stay in the body the more the body needs to do.

Also drinking water can help in the meantime. water is also a natural healer. Help is even around us without a doctor. But of course going to one is smart to do so when something is not going away.