Is there an approved otc allergy medication for my 18month daughter?

None: While there are no medications specifically approved for children in that age group, you physician can review your daugters symptoms and may be able to steer you to some helpful remedies. It would require someone reviewing her individual, overall health and symptoms. If she seems to always be stuff or congested, or has eczema, you need to see her doctor to help.

OTC Allergy Meds: Many antihistamines can be used in children, but the doses are not generally given for children under two. Benadryl (diphenhydramine) is most commonly used. Caution in the use, as they may cause sedation. The dose for Diphenhydramine is about 0.5 mg / pound. The common dose supplied is 12.5 mg / 5 cc. A twenty-five pound child would receive 12.5 mg or 5 cc. Best to see your child's pediatrician.