Is it safe to mix Claritin D with Dayquil?

I believe Dayquil has the nasal decongestant phenylepherine in it (please check the ingredients!) It may even have an antihistimine in it also. You CAN NOT double-up on antihistimines or decongestants. You can always ask your pharmacist which medication would help your symptoms better and they are usually the best people to ask about these medication interactions.