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Many holistic practitioners suggest sesame oil to be inhaled through the nose, but I must advise against it in your case. This is because it is not a good thing to get oil into the lungs, and it could prove damaging to a 5-year old. I would advise getting a humidifier, to moisten the air that the child inhales.
Yes the airborne fumes irritate the lungs and nasal passages
it can. If your sick sometimes your nasal passages get to dry, and that can cause them to bleed. Use saline nasal spray and see if it improves.
Dry nasal passages may crack, allowing bacteria to enter. When allergies are diagnosed, a number of nasal sprays are available to try to prevent inflammation within the nasal passageways, thus allowing the normal flow of mucus.
That dry feeling may not be dryness at all but an infection in the nasopharynx or, perhaps, the tonsils or adenoids. See a doctor.
Nasal sprays are used to treat a variety of health issues. The most common use is as a antihistamine to treat allergies. They can also be used as a decongestant to relive blocked nasal passages. Natural nasal sprays such as saline are used to moisturize dry or irritated nostrils.
When scabs are present in the nose it is usually due to dry air and lack of moisture in the nasal passages. If the nose is dry for an extended period it will crack and bleed causing scabs.
The nasal passages are supposed to create some moisture, but when there is drainage that doesn't actually drain, it will become dry. You can help prevent this by using a nasal saline spray or a neti pot. A neti pot is shaped similar to an Aladdin's lamp, with a spout that fits inside the nasal passage. You simply fill it with warm salt water, then with your head bent over and tilted to the side over the sink, you first flush one side, then do the other side the same way. This flushes allerges, etc. from the nasal passages, as well as excess mucous (more detailed instructions come with the neti pot). It also helps keep the nasal passages moist, which doctors recommend. But a bottle of nasal saline spray works well too, and can be taken with you and used anywhere. And both can be used as often as you need.
Sounds like you really just need to get hydrated--drink more water during the day, particularly if you work inside a building. For your nasal passages, there are several hydrating sprays you can find at the drugstore. Even plain saline ones work well.
There are many types of medicated nasal sprays, or nose sprays. Some of the most common include: antihistamine sprays, which help alleviate the symptoms of allergies; decongestant sprays, which can help open nasal passages; and saline sprays, which keep dry nares moist. There is also a flu vaccine that is administered intranasally.
It can dry your skin out.
The nose warms and moisturizes the air you breath in. It could be that the cool dry air coming directly from the mouth is drying the throat and irritating it. Alternately, it could be that the reason for the mouth breathing is that the nasal passages are stuffy and mucus from them is dripping into the throat at night when you lie back (post nasal drip). This can be irritating.
nasal spray