Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
fever, chills, body aches, flu symptoms, sores in your mouth and throat;
easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin;
headache with chest pain and severe dizziness, fainting, fast or pounding heartbeats;
sudden numbness or weakness (especially on one side of the body), sudden severe headache, slurred speech, problems with balance;
chest pain, sudden cough, wheezing, rapid breathing, coughing up blood;
problems with vision or hearing;
pain, swelling, warmth, or redness in one or both legs;
severe pain in your side or lower back, blood in your urine, little or no urine;
low blood sugar (more common in pregnant women)--headache, hunger, weakness, sweating, confusion, irritability, dizziness, fast heart rate, or feeling jittery;
loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
severe skin reaction -- fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain, followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.
Common side effects may include:
headache, blurred vision, changes in color vision;
sweating or flushing (warmth, redness, or tingly feeling);
mild dizziness, spinning sensation, ringing in your ears; or
upset stomach, vomiting, stomach pain.
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.
 Qualaquin side effects (more detail)
