If you have allergies, pregnancy can make your symptoms worse. But you're right to worry about taking allergy medicine during pregnancy. Pregnant women shouldn't take some allergy drugs. Certain antihistamines, however, are safe.
free radical. (chemistry). An atom or a diatomic or polyatomic molecule which possesses one unpaired electron. Also known as a radical.ree radical. in chemistry, a molecule or atom that contains an unpaired electron but is neither positively nor negatively charged. Free radicals are usually highly reactive and unstable.
2 (in chemistry) a reaction in which an atom, molecule, or radical is removed from combination and replaced by another. 3 (in physics) the displacing in space of one mass by another, as when the weight or volume of a fluid is displaced by a floating or submerged body.