I have been on phentermine 37.5 for two weeks. I take half of one pill each day. I started to break out in boils, acne all over my face and scalp a few days ago. I researched that this was called cystic acne and several users of phentermine have had the same reaction. However, its not listed as a side effect. The cysts, assuming thats what they are have migrated into my neck and are extremly painful. It looks like i have swollen glads. I have taken IBU to relieve the swelling but it has done nothing for the swelling and pain. I do not take any other medications. Today it is extremly swollen and painful and new lumps have developed in my neck. I am a healthy 32 year old mom. I have never had acne or experienced anything like this. I m very concerned.