A baby's first sniffles can be scary and confusing, especially when everyone from the nurse at your pediatrician's office to your mother-in-law spouts conflicting opinions. Cold? Flu? Sinusitis? Hay fever?
One thing's for sure: You can probably cross that last diagnosis off your list. "We rarely see inhalant allergies before 18 to 24 months of age," says Dale Umetsu, M.D., Ph.D., professor of pediatrics at Harvard Medical School and an allergist/immunologist at Children's Hospital Boston. "A baby might be genetically predisposed to develop an allergy to pet dander or tree pollen, but in order to become sensitized to these substances he has to inhale them over a period of time."
Food allergies and eczema can be present after birth, however, and may signal a tendency to develop asthma and inhalant allergies later. "We call it the 'allergic march,'" explains Michael J. Welch, M.D., author of The American Academy of Pediatrics Guide to Your Child's Allergies and Asthma (Villard). It starts with the gut and the skin, then moves on to the nose and the lungs. Dust mites are the most common early inhalant allergen, Welch says, followed by mold, pollen and pet dander—in that order.
There's not much you can do to stop the allergic march, though having a family pet might help. "There's a growing body of evidence that living with a dog or cat when you're an infant may moderately decrease the chances that you'll become asthmatic or generally allergic later in life," Welch says.