Is it a cold or allergy?
If you notice that your child always seems to have a runny nose (clear discharge), a slight cough and/or watery eyes, allergies, rather than a cold, might be the culprit. Try making your baby's room an allergen-free zone. Do not allow pets into the room. Get rid of stuffed animals, curtains and other allergen catching fabric. If possible, get rid of wall-to-wall carpet. Wash bedding frequently with scent-free detergent. Avoid perfumes and strong-smelling lotions or detergents for yourself as well.
Additionally, keep a detailed diary of your baby's diet to see if there is any correlation between what he eats and his symptoms. (If you are breastfeeding, keep a food diary for yourself as well.) If you see an improvement after making these changes, allergies might indeed be the problem. Talk to your child's pediatrician about ways to ease allergy symptoms.
As your child grows, you will come to recognize his symptoms and how he acts whether he is getting a cold or something more serious. In the meantime, don't panic. Keep things simple if you suspect a cold. A manual nasal aspirator used before feedings and at bedtime can offer tremendous relief for stuffed up babies. Warm baths in a steamy bathroom are soothing and relieve congestion as well. Placing a small pillow under the head of your baby's mattress will allow him to sleep with his head safely elevated, allowing for drainage. If you feel the symptoms are getting worse or have other concerns always call your pediatrician.
(Note: If your baby is under three months of age, contact your doctor even if you suspect it's just a cold.)