What type of medical condition is Doxycycline used to treat?

Doxycycline is an antibiotic that belongs to the tetracycline class and is widely used to treat a variety of bacterial infections. One notable condition it effectively treats is acne vulgaris. Acne is often caused by the overgrowth of the bacteria Propionibacterium acnes as well as inflammation. Doxycycline helps by reducing the bacteria and by exerting anti-inflammatory effects, which can improve the appearance of acne in many patients.

The other conditions listed—chronic liver disease, hypertension, and diabetes—are not treated with doxycycline. Chronic liver disease typically requires management strategies focused on the underlying cause, hypertension is generally treated with antihypertensive medications, and diabetes management involves insulin or oral hypoglycemic agents. Therefore, the association of doxycycline with the treatment of acne vulgaris is what makes it the correct choice among the options provided.