Can allergy medication cause kids to have temper tantrums?

Some may do: The effects of some allergy medication in children are specific to each kid. It is most known that kids with enough dose of Diphenhydramine become sleepy, but some kids become hyperactive. The explanation is in the histamine receptors in the brain. We are not all wired the same. This has not been reported in 2nd generation antihistamines, but I have seen this effect Cetirizine in very few cases.

Yes: Most allergy medications contain antihistamines which can cause behavioral changes, including temper tantrums. Sedation is the most common side effect but paradoxical reactions including hyperactivity and irritability are possible.

Maybe: Some antihistimines can cause your child to be somewhat sleepy and grumpy. May want to change to one of the non drowsy medicines.