Antihistamines, such as diphenhydramine (Benadryl) or chlorpheniramine, help block the actions of histamine, which causes symptoms of anaphylaxis. Long-acting antihistamines, such as loratadine (Claritin), tend to cause less drowsiness.

Diphenhydramine Dosing Chart

Age	Each Dose	Interval	Max Daily Dose
2-5 years	6.25 mg	4-6 hours	37.5 mg/day
6-11 years	12.5-25 mg	4-6 hours	150 mg/day
12 and older	25-50 mg	4-6 hours	300 mg/day

Chlorpheniramine Dosing Chart

Age	Each Dose	Interval	Max Daily Dose
Under 6	consult your physician
6-11 years	2 mg	4-6 hours	12 mg/day
12 and up	4 mg	4-6 hours	24 mg/day