I've been using the same batch of test prop for 6 months on and off.(short cycles).Anyway all this time injections go smoothly,except for the last 4-5 injections.At first i got a slight cough which came on pretty slow.As i progressed injections the cough would come on quicker and stronger.My guess is that it's my immune response.The question is why would i start developing an allergic reaction to the same substance i've been using for a long time?