I wonder if it’s increased metabolic rate. Allergy meds often raise blood pressure.
I know they can speed up heart rate, but that's the decongestant part (if combined), not the antihistamine. Didn't know about the blood pressure.
It is the decongestant present in many allergy meds that cause an increase in blood pressure and make some people lose their appetite. Never worked for me, or I would take a Sudafed every day!
The antihistamine part of allergy meds (bendaryl, claritin, allegra, zyrtec) have no effect on appetite, weight, or blood pressure, as far as I know.
One of the possible side effects of the allergy drug Tavist is increased appetite and weight gain. This is a little curious, since a freeper comment on another post about this subject thought the active ingredient in Tavist (clemastine fumarate) was chemically related to the 2 mentioned in this article.
Of course, in this study these drugs were injected, not taken orally, so that makes a huge difference. One of these drugs is present in OTC allergy eye drops (Alaway) and the other is present in an allergy nasal spray (Nasalcrom). I guess you would have to snort a lot of Nasalcrom to get any weight loss effect, though. ;-)