MAO inhibitor use is a contraindication. Somnolence is common in those taking the first generation antihistamines as is impaired performance at work and driving although this varies greatly. Dry mouth and blurred vision are also potential problems. Acetaminophen should not be used for long term treatment due to renal and hepatic impairment. Decongestants may cause irritability and sleeplessness and should not be used in those with hypertention .
Children especially are prone to hyperactivity and restlessness.
Some preparations contain phenylalanine . Most first generation antihistamines are available for children 6 to 12 years of age but not all preparations are available in liquid, drops, or chewable form. Under age 6 they are recommended only when advised by a physician. Under age 6 see your doctor. Children 1 mg.