Can I take Zyrtec D and Dayquil together?

Patient: I have been taking Zyrtec D for my allergies. But now I have a cold and need to take DayQuil. Is it ok to take the DayQuil? If not, how long should I wait after my last Zyrtec to take it or is there something else that I could take?

Doctor: Both Zyrtec D and Dayquil should not be taken together, since, they both have a decongestant and an anti-allergic component. Dayquil may be taken for common cold (in preference), but at least 12hrs after the last dose of Zyrtec D. I suggest you to visit your family Physician for further clinical assessment and advice.