re·act 
/riˈækt/ verb
re·acts; re·act·ed; re·act·ing /riˈækt/ verb [no obj] 1 : to behave or change in a particular way when something happens, is said, etc.
▪ When I told her what happened, she reacted with anger. ▪ I didn't expect him to react that way. ▪ The firefighters reacted quickly when they heard the alarm. — often + to ▪ She reacted to the news by getting angry. ▪ Most people reacted positively to the smoking ban. — see also overreact 2 of a chemical substance : to change after coming into contact with another substance — often + with ▪ The chemicals react with each other to form a gas. — often + together ▪ Ozone is formed in the atmosphere when sunlight and hydrocarbons react together. 3 medical : to be affected by a drug, food, etc., in usually a bad way
▪ He reacted badly to the drug.
▪ When I told her what happened, she reacted with anger. ▪ I didn't expect him to react that way. ▪ The firefighters reacted quickly when they heard the alarm. — often + to ▪ She reacted to the news by getting angry. ▪ Most people reacted positively to the smoking ban. — see also overreact
▪ He reacted badly to the drug.
react against [phrasal verb]
react against (someone or something) : to do things that are opposed to (something or someone that you disagree with)
▪ He belonged to a group of artists who reacted against convention by doing things in a completely new way.
▪ He belonged to a group of artists who reacted against convention by doing things in a completely new way.
