Read more: Effects of allergy medication on your child's behaviour Antihistamines are medicines used to treat allergy symptoms such as hay fever, itchy eyes, hives, stings and rashes, and allergic reactions to food.It can also relieve itching caused by chicken pox, eczema and insect bites.
Many antihistamines are available over the counter as tablets, syrups, nasal sprays, eye drops or ointments.
Several brands have paediatric versions, which are syrups specifically aimed at (and supposedly safe for) children.
According to a report of a patient in the Journal of Child and Adolescent Psychopharmacology in 2010, DPH is abused for its sedative, sleep-inducing, and euphoric effects on the central nervous system.
The antihistamines cause addiction by increasing dopamine release in the brain's reward and pleasure centers, typical of addictive substances such as Vicodin and heroin.
Older antihistamines, such as diphenhydramine (Benadryl), chlorpheniramine (Chlor-Trimeton), and hydroxyzine (Atarax), also work well but have many side effects.
Oral antihistamines work well when taken as-needed, meaning that allergy symptoms improve within an hour or two of taking the medication.
Some people deliberately choose to abuse antihistamines, often as a substitute when they can't get their drug of choice.
Others may start out using an antihistamine as a sleep aid but find they need higher and higher doses to fall asleep.
Earlier this year, we published a story about how certain allergy medication can react negatively with your child, even causing aggression, hyperactivity or anxiety.