Drowsiness

• Although cetirizine is one of the newer antihistamines which is not as likely to cause drowsiness as earlier products, it still causes drowsiness in up to 13 percent of people who take it, according to pre-approval clinical studies, as detailed by eMedTV.
  
  

Other Side Effects

• Other side effects for adults in the clinical studies included fatigue, dry mouth, sore throat and dizziness. These only occurred in 2 to 6 percent of participants.
  
  

Considerations with Children

• Side effects for children taking cetirizine differed from adults. The most common side effect for children was headaches, in up to 14 percent.
  
  

Other Side Effects in Children

• Children in the pre-approval clinical studies also experienced sore throat, abdominal pain, coughing, diarrhea, drowsiness and nosebleeds.
  
  

Serious Side Effects

• Cetirizine can cause some serious, but rare, side effects. These include confusion, anxiety, wheezing, difficulty breathing, difficulty urinating, high blood pressure, heart palpitations, rapid heartbeat or an increase in liver enzymes.