What medication can my 3 month old take for a cold

Cold and cough medicines for infants have been pulled from the markett, and are no longer manufactured because an extensive study by the FDA and the APA have shown them to not only be ineffective in children under 2, but also dangerous. I recommend a cool mist humidifier be placed in any room the baby occupies, as well as 10 minute steams in the bathroom a couple of times a day. If your baby is running a fever, or very fussy and the steams and humidifier aren't offering any relief, you will want to see your doctor.

I agree with Ruchele 100%
I also really like the vapor bath made by Johnson & Johnson. It works real good for my kids. Also if it is nasal congestion use an infant nasal saline mist to clean out the nose (with aspirator). Since the baby is too young to use Vicks vapor rub on their skin, you can put some on a tissue or cloth and hold it near the baby. Do not leave baby unattended with it! I always put it on a tissue or on my chest when feeding a bottle, changing a diaper, etc... That way it can help without actually using it on him.
Elevate the crib mattress on one side. You can roll up a towel and put under the crib head to help baby sleep at night. An elevated head will make it easier for baby to breathe.