That leaflet that comes with your pack of decongestants-- have you ever read them? Do you know what compounds are in your antihistamine, and most importantly, the side effects?

This article from Medical News Today highlights the possible side effects of some allergy medications. Here are some important points:

Some antihistamines can cause drowsiness or sleepiness. You should take this into consideration if you'll be driving or will be engaging in tasks that needs you to be fully alert. Some antihistamines have a drying effect and cause annoying effects like dry mouth. Not a good choice if you're up for a job interview or a speech, eh? And some have really serious side effects in certain individuals:

Some patients with high blood pressure may experience problems due to the decongestants included in many allergy products. Decongestants can raise blood pressure, which can be particularly dangerous in patients with high blood pressure that is not well controlled, says Hussar.

Some allergy products contain analgesics such as acetaminophen or ibuprofen. This should be noted especially by those who take other medications, in case their other medicines also contains analgesics.

When an allergy product containing one of these analgesics as a secondary ingredient is taken by a patient who is also using an analgesic for another purpose, an excessive response may result. Side effects may be subtle and develop slowly but, in some individuals serious stomach, kidney, or liver problems could result.

If in doubt, or if you want alternative medications, consult your pharmacist or doctor.