Fourth, the FDA removed several allergy and cold relief medications that contain antihistamine or decongestant for children less than 6 years of age because of reported overdoses. There were accounts of some antihistamines causing extreme drowsiness. Oral decongestants were reported to place young children at higher risk of tachycardia (racing of the heart), palpitations, insomnia, irritability and tremor (and this is not a complete list). It was concluded that young children may be more vulnerable to the potential side effects of OTC allergy drugs. Errors in dosing and in some cases intentional dosing above recommended guidelines resulted in serious injury.
OTC allergy medications may be effective and safely used when dosage guidelines are followed. Over dosing should be strictly avoided. This means you should read the package insert or written dosage guidelines carefully. Maximum allowed doses vary based on age, other medications being taken at the same time and health status of your liver and kidneys.
Although newer antihistamines have a lower risk of drowsiness, doses taken above the recommended levels may cause not only drowsiness but other serious side effects. If you have questions or are uncertain about how a medication should be taken talk to your doctor or pharmacist.
Are you happy about previously prescribed allergy medication going OTC?
See also:
How to choose the best allergy medicine

7 Tips for Dealing with Seasonal Allergies
Are You Allergic to These 10 Everyday Items?
10 Things to Know About Food Allergies in the Classroom
Seasonal vs. Year-Round Allergies