If food allergies run in either parent's family, you may be concerned that your baby is displaying symptoms of an allergy to infant formula. Although allergies to baby formula are uncommon--the U.S. Department of Agriculture puts the number of babies who develop an allergy to milk protein, the base of most infant formula, at less than 3 percent of U.S. infants--some babies do develop them. Half of those that have allergic reactions to milk-based baby formula are also allergic to soy, which is the other main food base of infant formula. If your baby does have signs of an allergy to milk formula, talk to your baby's doctor. There are hypoallergenic formula options that may help. Here are some symptoms of infant formula allergy to look for. Oh--and if it turns out your baby is having an allergic reaction to infant formula, don't stress it--within a few years, most children grow out of infant cow's milk allergies.

In babies, an allergic reaction to infant formula often occurs on the skin.  Look for

• hives
• eczema (flaky, dry patches on the skin)
• ring around the rectum that diaper rash cream doesn't help
  
• other rash
  

Expect your baby to spit up sometimes, particularly in the early months.  Babies have immature digestive tracts and normally spit up occasionally.  But take note if your baby is:

• having repeated vomiting episodes
  
• having episodes of forceful vomiting (projectile vomiting)
  
• spitting up formula a lot, an indication that your baby may have excessive reflux
  

Your baby's stools may indicate an allergy to cow's milk protein or soy.  Note if the stools:

• smell foul
• are unusually hard (constipation)
  
• are unusually loose (diarrhea)
• are frequently loose (diarrhea occurring multiple times in a day for several days) - CALL THE DOCTOR
  
• blood in the stool - CALL THE DOCTOR
  

Note: it's normal for a baby's poop to change appearance and smell when you switch from breast milk to infant formula.

Abdominal discomfort--that is, tummy pain--can be a sign of an allergy to infant formula.  Watch for these symptoms:

• Your baby fusses, cries, and squirms during or after a feeding
• Your baby cries a lot, seems gassy, or shows other signs of colic

The symptoms may, however, not be indicative of a baby formula allergy at all, but again be due to the baby's immature digestive tract or some other problem.

Note: Lactose intolerance, while possible, is actually quite uncommon in babies, according to the U.S. Dept. of Agriculture.

An allergic reaction to milk protein may be indicated by these symptoms if they present when your baby does not have a cold virus:

• nasal congestion
• wheezing / asthma
• shortness of breath
• throat mucus
• nose mucus
• other breathing problems or abnormalities of the respiratory passages
  

As a result of other symptoms, in particular excessive vomiting or frequent diarrhea, your baby's growth may slow down.

Watch for this sign of a possible food allergy. If you suspect failure to thrive, don't hesitate--talk to your baby's pediatrician right away.

Also let your physician know if you're concerned your baby is gaining too much weight--not so your doctor can put your baby on a diet, but to see if there is an underlying allergy or condition.

An infant formula allergy can manifest itself in part in discomfort that may keep a baby from sleeping soundly.

If your baby shows any of the above symptoms and you are concerned that she is allergic to infant formula or might have another health problem, talk to her pediatrician.

Don't let this article serve as medical advice--it's just meant as a guideline to help you know what to look for if you're concerned about a possible allergic reaction to infant formula.