moving more will speed up your metabolism.
Yes, cayenne pepper does speed up your metabolism, all chili peppers due because of the chemical capsaisin, which is what makes chili peppers hot, however, the effect only lasts for about 20 minutes at a maximum of 20 percent and the results are negligible. If you added cayenne pepper to every meal, every day, it wouldn't equate to no more than a 100 calories or so a week, so not really even worth straining yourself over, however, capsasin is very healthy overall in moderation, so I consume plenty of it regularly. The best "quick fix" for metabolism is caffeine, from any substance (I.E. coffee, green tea), but to naturally increase your metabolism you have to workout and increase muscle mass.
The side effects of allergy medications keep some people from using them. Natural remedies can be a great alternative, but some are more effective than others.