**Core Concept**
Cluster headaches are a type of primary headache disorder characterized by recurrent, severe, and short-lived attacks of unilateral orbital or periorbital pain. These headaches often occur at the same time of day and are typically accompanied by autonomic symptoms such as lacrimation, nasal congestion, and ptosis.

**Why the Correct Answer is Right**
The patient's symptoms of headache on awakening, nasal stuffiness, and reddening of the eye are highly suggestive of cluster headaches. This specific pattern of symptoms is often referred to as a "cluster headache attack." Cluster headaches usually occur in clusters or cycles, with multiple attacks occurring at the same time each day over a period of several weeks or months. The exact pathophysiology of cluster headaches is not fully understood, but it is thought to involve a complex interplay between genetic, environmental, and hormonal factors.

**Why Each Wrong Option is Incorrect**
**Option B:** Tension headaches are typically characterized by a band-like or squeezing sensation around the forehead, which is not consistent with the patient's symptoms. Tension headaches also tend to be bilateral and are often associated with neck or shoulder tension.
**Option C:** Migraines are a type of primary headache disorder that is typically characterized by a unilateral, pulsating headache that is often accompanied by nausea, vomiting, and sensitivity to light and sound. While migraines can occur at any time, they are not typically associated with nasal stuffiness or reddening of the eye.

**Clinical Pearl / High-Yield Fact**
Cluster headaches are often referred to as "suicide headaches" due to their intense and debilitating nature. Patients with cluster headaches may experience significant distress and impairment in daily activities during active periods.

**✓ Correct Answer: A. Cluster headache**