The so called 'tren cough' or 'Fina cough' is well known amongst many tren users. Some users seem to get the cough following every injection; others never or extremely rarely will get the cough. Usually it is manifested upon injection, with a tightness in the chest, and a metallic taste in the back of the mouth, followed by an uncontrollable violent cough which can be quite frightening, as anyone who has experienced it will tell you, whether it's for the first time or not. There have been some very elaborate theories about the reasons for getting the cough from trenbolone, some of which have had mechanisms involving molecules that only trenbolone affects resulting in bronchioconstriction, etc. However, the fact remains that many users have also experienced the same cough from steroids such as equipoise and testosterone cypionate. In addition, these mechanisms that are proposed are highly unlikely to occur immediately upon injection, as that is too fast a timescale for the proposed mechanism. Thus it must be the result of something entering the blood stream and traveling to the lungs for the cough to be manifested that quickly.
This leads us onto the next theory suggested by many which is that trenbolone is produced by many UGLs, and as such is made with higher percentages of Benzyl Alcohol (BA) than pharma grade products are, and it is the alcohol that is causing the reaction. The only problem with this theory is that trenbolone is made by most UGLs with the same BA percentages as things such as testosterone propionate, and nandrolone decanoate. If it was purely the BA concentration, than we would expect to see the cough with these other products as well, which we do not. Thus, as we have eliminated the oil, solvents and carriers, it leaves us with the Trenbolone product itself as the potential culprit.