Recurrent Acute Tonsillitis: This is the most common cause of relapsing tonsillitis, often due to recurrent infections with Group A beta-hemolytic streptococcus (GABHS) or other bacteria, and sometimes viruses. The recurrent nature suggests a possible issue with the immune system's ability to clear the infection or an anatomical issue predisposing to infection.

Tonsillar Carriage of Pathogens: Some individuals can be chronic carriers of pathogens like GABHS, leading to recurrent infections.
Allergic Rhinitis or Sinusitis: Underlying allergic conditions can lead to chronic inflammation and increase the risk of tonsillitis.
Anatomical Abnormalities: Enlarged tonsils or other anatomical issues can predispose to recurrent infections.
Immunodeficiency: Mild immunodeficiencies might not be immediately apparent but can increase susceptibility to recurrent infections.

Peritonsillar Abscess: A serious complication of tonsillitis that can lead to severe consequences if not promptly treated.
Lemierre's Syndrome: A rare but potentially life-threatening condition following a tonsillar infection, characterized by septic thrombophlebitis of the internal jugular vein.
Rheumatic Fever: A complication of untreated streptococcal tonsillitis that can lead to heart valve damage.
Post-streptococcal Glomerulonephritis (PSGN): A kidney disease that can occur after streptococcal infections, including tonsillitis.

Tonsillar Malignancy: Although rare, malignancies such as lymphoma can present with symptoms mimicking recurrent tonsillitis.
Granulomatosis with Polyangiitis (GPA): A form of vasculitis that can affect the respiratory tract and present with recurrent infections or inflammation.
Cystic Fibrosis: A genetic disorder that can lead to recurrent respiratory infections, including tonsillitis, due to thickened mucus.
Primary Immunodeficiency Diseases: Conditions like Selective IgA deficiency or Common Variable Immunodeficiency can increase the risk of recurrent infections.