Allergic Rhinitis: This condition is characterized by an allergic reaction to airborne allergens such as pollen, dust mites, or pet dander, leading to symptoms like sneezing, runny nose, and headaches due to sinus pressure.

Sinusitis: Inflammation or infection of the sinuses can cause headaches and sneezing, among other symptoms like facial pain and nasal congestion.
Common Cold: Viral upper respiratory infections can lead to sneezing, headache, and other symptoms like cough and sore throat.
Hay Fever: Similar to allergic rhinitis, hay fever is an allergic reaction to outdoor allergens like pollen, causing symptoms including sneezing and headache.

Meningitis: Although less common, meningitis (inflammation of the protective membranes covering the brain and spinal cord) can present with headache and, in some cases, sneezing, along with more severe symptoms like fever, stiff neck, and confusion. It's critical to diagnose promptly due to its potential for severe consequences.
Encephalitis: Inflammation of the brain tissue, usually caused by viral infections, can lead to symptoms including headache, and in some cases, may involve sneezing, along with more severe neurological symptoms.

Cerebral Vasculitis: Inflammation of the blood vessels in the brain can cause a variety of symptoms, including headache, and potentially sneezing if it affects areas related to nasal or sinus function.
Eosinophilic Granuloma with Polyangiitis (Churg-Strauss Syndrome): A rare autoimmune condition that can affect various parts of the body, including the respiratory system, and may present with symptoms like sneezing and headache among others.