For antihistamines to be most effective they should be taken before an allergic reaction takes place. Antihistamines are available in oral liquid, tablet, and capsule forms as well as injectable preparations.
Decongestants are available in oral and spray forms.
Occasional switching of preparations or combining of agents may be effective in relieving symptoms no longer helped by the previous medications. Rarely, constipation and urinary difficulties occur. With time, these side-effects usually improve . Be careful that these other medications are not taken while you are taking Seldane. If side-effects occur with decongestants, the more common include nervousness, insomnia, increased heart rate and blood pressure, as well as general stimulation.