Doxycycline is a broad-spectrum antibiotic that's commonly used in medical and veterinary fields. It belongs to the tetracycline class of antibiotics and is used to treat a variety of bacterial infections, including respiratory infections, skin infections, intestinal infections, and others. Doxycycline may also be used to prevent malaria and is sometimes given to travelers who are visiting areas where malaria is common. It works by inhibiting the growth and reproduction of bacteria. If you have questions about a medical condition or treatment, you should always consult with a healthcare professional.