Get emergency medical help if you have any signs of an allergic reaction to doxycycline: (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning in your eyes, skin pain, red or purple skin rash that spreads and causes blistering and peeling).
Seek medical treatment if you have a serious drug reaction that can affect many parts of your body. Symptoms may include: skin rash, fever, swollen glands, flu-like symptoms, muscle aches, severe weakness, unusual bruising, or yellowing of your skin or eyes. This reaction may occur several weeks after you began using doxycycline.
Call your doctor at once if you have:
severe stomach pain, diarrhea that is watery or bloody;
throat irritation, trouble swallowing;
chest pain, irregular heart rhythm, feeling short of breath;
little or no urination;
low white blood cell counts - fever, chills, swollen glands, body aches, weakness, pale skin, easy bruising or bleeding;
severe headaches, ringing in your ears, dizziness, nausea, vision problems, pain behind your eyes;
loss of appetite, upper stomach pain (that may spread to your back), tiredness, nausea or vomiting, fast heart rate, dark urine, jaundice (yellowing of the skin or eyes).
Common doxycycline side effects may include:
nausea, vomiting, upset stomach, loss of appetite;
mild diarrhea;
skin rash or itching;
darkened skin color; or
vaginal itching or discharge.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Doxycycline side effects (more detail)
