Diphenhydramine (Benadryl) is an allergy medication, though children may take it for coughs, as a sleep-aid, for motion sickness and as an addition to epinephrine in a severe allergic reaction. It is an H1 antihistamine, which means that it blocks the H1 histamine receptor; this is how symptoms of itchiness, sneezing and runny nose are improved. Children can take diphenhydramine by mouth as a pill or a liquid, use it on itchy skin as a cream or lotion or have it injected into a vein or muscle. Several potential side effects could occur in children taking diphenhydramine.
Effects on the Central Nervous System
The most common side effect of diphenhydramine is sedation, which is why it may also be used as a sleep aid. According to the online pharmacology database MicroMedex, the onset of sleepiness generally occurs within one to three hours of first taking a dose, and may last from four to seven hours. Another effect on the central nervous system is dizziness.
Effects on the Circulatory System
Children on diphenhydramine may notice a faster heartbeat than usual; in addition, their blood pressure may be lower than normal. Children may notice that they can actually feel their heart beat quickly--this is called "palpitations," and is another potential side effect of diphenhydramine.
Effects on the Skin
Diphenhydramine may, paradoxically, cause hives, which are often itchy. In addition, children may experience a rash, and may be more sensitive to sunlight. Consequently, parents should be careful to properly protect exposed areas of skin with sunscreen, hats and clothing to avoid sunburn.
Effects on the Digestive System
Nausea, vomiting and constipation are potential side effects. Because of the H1 receptors in the mouth, children may experience a dry mouth and throat. A lack of appetite and general feeling of stomach discomfort may also be part of the digestive system side effects caused by diphenhydramine.
Effects on the Urinary System
Unfortunately, because antihistamines don't just work on allergy symptoms, other parts of the body may be affected as well. University of Illinois College of Medicine professors Randal Skidgel, Ph.D. and Ervin Erdos, M.D., writing in the pharmacology textbook "Goodman and Gilman's Pharmacological Basis of Therapeutics," note that children on diphenydramine may experience pain while urinating or may find they have the urge to urinate but not be able to do so; this is called urinary retention. Alternatively, children may suffer from urinary frequency, which is the feeling that one has to go to the bathroom more frequently than usual, but little or no urine comes out.
Other Side Effects
Rarely, children on diphenhydramine experience problems with their blood cells (disorders called aplastic anemia, thrombocytopenia and hemolytic anemia). Other side effects may include dryness in the nose; a tremor; strange sensations in the hands, such as numbness or tingling; blurry vision; wheezing; and a feeling of tightness in the chest.
References
- "UpToDate"; Denise S. Basow; 2010
- MicroMedex: "Diphenhydramine"
- "Goodman & Gilman's The Pharmacological Basis of Therapeutics"; Laurence L. Brunton et. al.; 2006
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