Rumex crispus is useful in Cough with a tickling in the pit of the throat and behind the sternum. A cough barely relieves tickle, long episodes of dry, teasing, hacking, fatiguing cough, little expectoration. tenacious mucous, cough on going from warm room to cool air, cough prevents sleep. 

It is a remedy for extreme sensitivity to cold air. 

The inspiration of cold air is, therefore, the provocative factor for the disease of the upper respiratory organs, calling for this remedy. The affinity of Rumex is mainly to the mucous membrane of the larynx, and the trachea and bronchi. 

The typical complaint about Rumex is the dry, incessant, violent and nonproductive cough which is excited by tickling behind the sternum and is severely aggravated by exposure to cold air. 
 
Use under medical supervision.