I have taken Ketotifen 3 days altogether. It is definitely giving me more brain fog and a lot of tiredness. I don't think I can manage a whole 40 days with those symptoms so I've stopped it for now. On the plus side, it is the only anti histamine that not bothered my stomach. I believe it would probably have helped IBS if I had the stamina to stick it out. Also my rhinitis improved a bit. I'm putting it aside. I hope others are doing better on it.