The Sharpless epoxidation reaction is one of the premier enantioselective chemical reactions. Histamines are proteins associated with many allergic reactions. This could result in allergic reactions including asthmatic reactions. One of the proteins that trigger allergic reactions is tropomyosin. Cockroaches are linked with allergic reactions in humans. Many proteins are enzymes that catalyze the chemical reactions in metabolism. Aldehydes are highly reactive and participate in many reactions. Proteins that act as catalysts in biochemical reactions are called enzymes. Many physical chemists specialize in exploring and proposing the mechanisms of various chemical reactions. Food allergies rarely cause respiratory (asthmatic) reactions, or rhinitis. Entropy is equally essential in predicting the extent and direction of complex chemical reactions. Proteins are functional macromolecules responsible for catalysing the biochemical reactions that sustain life. Water is essential for all the major chemical weathering reactions. Arenes are reactants in many organic reactions. Nervousness, skin reactions, and anaphylaxis have been reported.