Q. I used to find that over-the-counter allergy medicines made me sleepy. Now they usually keep me awake. Is there an explanation for this?
A. There are two possibilities. Many manufacturers of allergy remedies now include decongestants in some of their formulas. Ingredients like pseudoephedrine and phenylephrine can be stimulating and cause insomnia for some people. Unless you check the label you might not realize your allergy medicine has an unexpected addition.
One tip-off that your allergy medicine has a decongestant is the letter “D” in the name. For example, Allegra-D, Claritin-D or Mucinex D all contain pseudoephedrine. That is no guarantee, though. Actifed and Sudafed also contain pseudoephedrine. This drug can leave some people quite stimulated and awake for hours.
Another explanation for your reaction to allergy medicine might be that your nervous system may have changed. Many children and some adults react to antihistamines with restlessness and wakefulness rather than drowsiness. You might want to experiment with different antihistamines to find one that doesn’t keep you awake.