The sinuses are air-filled cavities located in the bones of the face and skull that connect to the nasal passages. When blood appears in the mucus or drainage, most episodes of blood-tinged nasal discharge stem from the highly sensitive lining of the nasal cavity, a condition known medically as epistaxis. While true sinus bleeding is much less common, it can occur due to specific underlying conditions.
Understanding the Anatomy: Nasal Passages Versus Sinus Cavities
The nasal passages are the two channels running from the nostrils to the back of the throat, and they are lined with a specialized mucous membrane. This lining is extremely rich in blood vessels, particularly in the anterior (front) part of the septum, an area often called Kiesselbach’s plexus. Because these small vessels lie close to the surface, they are easily damaged by trauma, dryness, or inflammation.
The paranasal sinuses—the frontal, maxillary, ethmoid, and sphenoid—are air-filled extensions that surround the nasal cavity. Their vascular supply is less dense and less exposed than the nasal passages. Sinuses drain mucus into the nasal cavity through small openings called ostia. For blood to originate deep within a sinus and exit through the nose, the bleeding source must either be significant enough to travel through the drainage pathway or be located near the ostia.
Common Reasons for Blood-Tinged Mucus
The vast majority of bloody nasal discharge is not a cause for alarm and occurs due to minor irritation of the nasal passage lining. Low humidity or dry air is the most frequent culprit, causing the delicate nasal mucosa to dry out, crack, and bleed slightly. The fragile blood vessels in the anterior nasal septum become brittle and easily rupture.
Aggressive actions like forceful nose blowing or frequent nose picking can physically damage the superficial blood vessels, leading to minor bleeding that mixes with mucus. Infections, such as the common cold or influenza, also cause inflammation and swelling of the nasal lining. This heightened sensitivity, combined with the repeated blowing required to clear congestion, often results in blood-streaked mucus.
Even seasonal allergies can contribute to this issue, as the repeated sneezing and congestion weaken the vessel walls. Certain topical nasal sprays, particularly decongestants used over a prolonged period, can also irritate and dry out the nasal lining. This superficial bleeding is typically self-limiting and stops quickly once the irritation ceases.
Conditions That Cause True Sinus Bleeding
Bleeding that originates from the deeper sinus cavities is less frequent and generally associated with more localized or chronic pathology. Severe or chronic sinusitis involves long-term inflammation of the sinus lining, which can cause the mucosal tissue to become fragile and ulcerated. The resulting irritation may cause the underlying blood vessels to bleed, especially if pressure builds up within the sinus.
Abnormal tissue growths like nasal polyps, which are non-cancerous, soft, teardrop-shaped growths, can cause bleeding if they become significantly large or are irritated. Bleeding may also occur after functional endoscopic sinus surgery (FESS), where the sinus lining is intentionally manipulated to widen the drainage pathways.
In rare instances, bleeding originating deep within the sinuses can be a sign of a benign or malignant tumor. Growths such as inverting papillomas or carcinomas, while uncommon, can be highly vascular and cause recurrent, persistent bleeding that is not easily resolved. These growths cause damage to the sinus walls and surrounding structures, leading to a more substantial bleed than simple nasal irritation.
Warning Signs and When to Seek Medical Care
You should seek care if the bleeding is heavy or if a continuous flow of blood lasts for more than 20 minutes, despite applying direct pressure. Recurrent episodes of bleeding that cannot be attributed to minor trauma or dryness warrant a visit to a healthcare provider for a thorough examination.
Bleeding that is consistently associated with other symptoms, such as persistent facial pain, pressure, or numbness, should be investigated. Unexplained changes in vision, a bulging eye, or bleeding that drains down the back of the throat (posterior bleed) are also red flags. Medical attention is necessary if you are taking blood-thinning medication or have a known blood-clotting disorder, as these conditions can complicate even minor bleeding events.