The following undesirable effects have been reported: In adults and children 12 years and older:
Drowsiness/sleepiness; Excessive tiredness; Dry mouth; Sore throat; Dizziness; Headache; Nausea.
In children 6 to 11 years old:
Headache; Sore throat; Stomach pain; Coughing; Drowsiness/Sleepiness; Diarrhea; Bronchospasm (sudden, uncontrolled narrowing of airways in lungs); Epistaxis (nose bleeding); Nausea; Vomiting.
The following rare events have been reported but it is not known whether they are directly related to cetirizine use.
Ataxia (uncontrolled muscle movement, incoordination), confusion, abnormal thinking, agitation, amnesia, anxiety, convulsions, depersonalization (alteration in the perception of the self so that the usual sense of one's own reality is lost), depression, dysphonia (difficulty in speaking), emotional lability (emotional instability), euphoria (an exaggerated unrealistic sense of well-being), impaired concentration, insomnia/sleep disorders, nervousness, hyperesthesia (increased sensitivity to any stimulation), hypoesthesia (abnormally decreased sensitivity), hyperkinesia (hyperactivity), hypertonia (muscle stiffness), migraine, myelitis (inflammation of the spinal cord), paralysis, paresthesia (abnormal sensation, such as burning, prickling, or tingling), ptosis (drooping of eyelids), syncope (fainting/temporary loss of consciousness), tremor, twitching, vertigo.
Palpitation, tachycardia (rapid heart rate), increased blood pressure, chest pain, heart failure, rarely decreased blood pressure.
Bronchitis, dyspnea (shortness of breath), hyperventilation (rapid breathing), increased sputum, pneumonia, respiratory disorder, rhinitis, sinusitis, upper respiratory tract infection.
Anorexia (loss of appetite), increased appetite, increased salivation, tongue discoloration, swelling of tongue, tooth caries, taste loss, taste perversion, dyspepsia, gastritis, stomatitis/ulcerative stomatitis (sores in the mouth), enlarged abdomen, eructation (burping), flatulence (gassiness), constipation, melena (black stools caused by bleeding in the stomach or small intestine), rectal bleeding, hemorrhoids.
Genitourinary and Renal:
Cystitis (inflammation of the urinary bladder), dysuria (painful urination), hematuria (blood in the urine), polyuria (excessive urination/frequent urination), urinary incontinence (inability to control urination), urinary retention (difficulty urinating), urinary tract infection, glomerulonephritis (inflammation of the kidney).
Dysmenorrhea, intermenstrual bleeding (bleeding between two menstrual periods), female breast pain, leucorrhea (whitish vaginal discharge), menorrhagia (heavy menstrual bleeding), decreased libido, vaginitis (inflammation of the vagina).
Hepatitis and increased liver enzymes (e.g, aminotransferases, bilirubin).
Ocular (Eye) and Otic (Ear):
Visual problems, blindness, conjunctivitis (irritation and redness of the thin membrane covering the eye), eye pain, glaucoma, loss of eye accommodation, eye bleeding, periorbital edema (accumulation of fluid surrounding the socket of the eye), xerophthalmia (dry eye), deafness, otalgia (earache), ototoxicity (toxicity to the ears), tinnitus (ringing in the ears).
Acne, alopecia (baldness), angioedema (rapid swelling of the skin), bullous eruption (large blisters), dermatitis (skin inflammation), dry skin, eczema, furunculosis (boils), hyperkeratosis (thickened skin), hypertrichosis (excessive hair growth), increased sweating, light sensitivity, pruritus (itchiness), purpura (small purple-red marks in skin), urticaria/rash, seborrhea, skin disorder, skin nodule.
Arthralgia (joint pain), arthritis, arthrosis/osteoporosis, muscle weakness, myalgia (muscle aches), asthenia (weakness), malaise (feeling of bodily discomfort), leg cramps.
Other undesirable effects:
Anaphylaxis (rare, life-threatening allergic reaction), back pain, cholestasis (inflammation of the gall bladder), dehydration, diabetes mellitus, swelling (generalized, facial, leg, or peripheral), fever, increased weight, lymphadenopathy (swelling of the lymph nodes), pallor, rigors (shaking), hemolytic anemia (anemia resulting from destruction of red blood cells), thrombocytopenia (decreased number of platelets), parosmia (distorted sense of smell), thirst.