The symptoms of hay fever include: 1  frequent sneezing. 2  runny or blocked nose. 3  itchy, red or watery eyes (allergic conjunctivitis)  an itchy throat, mouth, nose and 1  ears. cough, caused by postnasal drip (mucus dripping down the throat from the back of the nose)
Definition. noun, plural: chemical reactions. A process in which one or more substances (reactants) are chemically changed into one or more new substances (products).Chemical changes may involve motion of electrons in the forming and breaking of chemical bonds.Supplement. process in which one or more substances (reactants) are chemically changed into one or more new substances (products). Chemical changes may involve motion of electrons in the forming and breaking of chemical bonds. Supplement.
Define photochemical reaction. photochemical reaction synonyms, photochemical reaction pronunciation, photochemical reaction translation, English dictionary definition of photochemical reaction. Noun 1. photochemical reaction - a chemical reaction produced by the action of light chemical reaction, reaction - a process in which one or more substances... Photochemical reaction - definition of photochemical reaction by The Free Dictionary