Dr. Rassman,
Thanks again for maintaining this blog. I have asked a number of questions before and appreciate your prompt responses. I have a few questions about minoxidil and propecia. Here they are:
- I have been using minoxidil (liquid solution) for almost a year. A couple of months back it really started to irritate my scalp. I am almost convinced that it is a reaction to an ingredient i even here) that people have reported increased shedding after switching from the solution to the foam. Is there any explanation for this? Do you think it can hapn the solution that is not in rogaine foam because I have tried using the foam and it doesn’t irritate my scalp at all. I want to switch to the foam completely, but have read elsewhere (maybepen?
- If I do have an allergic reaction to an ingredient in the solution, will that inhibit its ability to work? In other words, does the irritation prevent the minoxidil from re-growing hair or preventing further loss? I do note that sometimes after I brush my hair when the solution has dried (8-6 hours later), large flakes and hairs fall off my head (though not an alarming amount of hair).
- Can I use Rogaine Foam in the morning and the solution at night? I figure if I use the solution only once a day and wash it off in the morning it may not irritate my scalp as much.
- I take propecia in the morning, first thing when I wake up. I also go running in the morning, right after I wake up. I know that exercising will not prevent propecia from working, but my concern is related to the timing. If I take propecia, then immediately begin to exercise, will I somehow decrease its ability to work? For example, will I sweat some of the medication out before it begins working?
- You are probably right that your irritation is from the non-active ingredient in the minoxidil. There is your explanation! Many people have said this as well. So try using Rogaine Foam. You’ve tried it and it doesn’t irritate your scalp, so there’s the solution!
- If you get irritation from minoxidil, you should stop taking it, switch to a lower dose, or change the formulations (to a foam for example). What you are reporting is not a good finding, but for the flaking, maybe the foam will solve that problem or the amount of minoxidil you apply should be at a reduced volume. If you have an allergic reaction to something then you should not use it anymore. You shouldn’t be thinking about if the irritation is preventing minoxidil from working! You should NOT be using it.
- Use Rogaine Foam as directed on the bottle, which is twice a day. Most people use it once in the morning and once at night… unless you want to use it once in the afternoon and once when you wake up in the middle of the night.
- If you are worried about “sweating out” the Propecia when you exercise, then take it after you exercise. I do not, however, believe that this is a problem.
I couldn’t say whether what you experienced is from the power of suggestion or if the Propecia had a physiological impact. That being said, the psychological aspect can be powerful (see 
If you’re taking finasteride, blood donation is bad for recipient women who are pregnant due to the risk of birth defects… and that is why it is banned for blood donors. I don’t know about tagging the blood in the donation process. Finasteride users are supposed to wait at least a month after the last dose and dutasteride users should wait at least 6 months before donating blood.
Elocon (mometasone) is a topical steroid and there is plenty of information on the 
Minoxidil was originally a not-that-great oral high blood pressure medication called Loniten. The results varied in the treatment of high blood pressure and eventually the medication was turned into a topical after the hair growth side effect was noticed. The drug stays in the plasma for about a 4 hour half life, but on the skin it stays much longer with slow absorption suggesting that once a day application may be satisfactory.
I’ve written about 