Brief Answer:
you should be investigated and examined in details at first...

Detailed Answer:

Hello,

First of all, please note that there are several different causes for these, so a proper medical check-up, as well as ENT, check up is necessary to diagnose the exact pathology.

Since this is happening quite sometimes now, it can be due to seasonal changes or even some causes. But the fact that it happens spontaneously (sometimes without any touching, sometimes during brushing or even during physical exertion) warrants for some further work-up regarding.

It's important to eliminate any medical conditions like Hypertension, prolonged dehydration, some nasal pathologies (particularly involving the nasal turbinates i.e. the humidity and temperature regulator of the nose). You should also get a few investigations eg. CBC, Peripheral blood smear, Electrolytes, LFT, Coagulation profile and ESR done.

You should start using a humidifier during sleeping. Additionally, I'd suggest you take steam inhalation three times daily for the time being. Avoid any direct Hot/Dry/cold air exposure.

You may also put plain Saline (0.9%) Nasal Drops 2drops in both nostrils thrice daily for the next few days and observe how you stay. The main purpose is to keep the nasal mucosa moisturized. I'd recommend, applying plain Parrafin gel in-around additionally and keep a note on the day to day progress.

Use Ultra-soft bristles toothbrush...do chlorhexidine gurgle twice daily for next few days... Dehydration, too much consumption of caffeine, smoking can all worsen this further, please avoid them if at all do. Drink plenty of water throughout the day.

If despite these, it remains persistent, then I'd suggest getting an ENT check-up done to look into it further and management accordingly...

Let me know if there're any further doubts/queries...

Take Care
Kind Regards

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