Thank you for your inquiry.
No, I have never come across sweating specifically of the scalp associated with asthma episodes, nor am I aware of any clinical significance of this observation. A search of the literature also failed to detect any reports of sweating specifically limited to the scalp in association with asthma exacerbations.
I did, however, find two curious reports, and have included the links to these in case you wish to take a look at them. One is an article from Thorax which looks at nonrespiratory symptoms of acute asthma. Sweating is listed as a premonitory event in some patients who experienced asthma episodes. However, this of course is not unusual, and has been shown as well that profuse diaphoresis is associated with severe events. The other link is from a lay website, and is a survey of asthma patients which shows a link between sweating per se and the condition of asthma (not necessarily related to asthma episodes).
Outside of these references noted above, I could find nothing of significance to help you with your inquiry. The only other thing I might mention is that I have had one patient with asthma and Frey syndrome (auriculotemporal syndrome). However, these two entities existed separately, occurring by coincidence in the same patient. From your description, it does not appear that your patient has Frey syndrome, but I mention it parenthetically in case you may not have considered it.
Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.