A: Christine, many babies have reactions to citrus fruits. Some are true allergic reactions involving the immune system, but most are simply skin irritations caused by acid and oils in the fruit. Since babies' mouths and skin are so sensitive, and irritations are common, it's recommended to wait until after a baby is 1 year old to try citrus fruits.

It can be hard to tell whether your baby's reaction to citrus is an allergy or irritation. Both can lead to mouth sores, swollen lips and a red rash around the mouth shortly after eating the fruit. But in addition to skin reactions, true allergic reactions can also involve the gastrointestinal, respiratory and cardiovascular systems, leading to other symptoms including swelling of the tongue and throat, vomiting, diarrhea, hives, itching, runny nose, wheezing, coughing, difficulty breathing and rarely even loss of consciousness. True allergies are also more common in children if one or both parents have them, since they tend to be hereditary.

To confirm whether your son has a true allergy to citrus fruit (and maybe other allergies as well), your doctor needs to do a blood test for allergies or refer your son to an allergy specialist for skin tests. If your son does have a citrus allergy, the doctor can help you plan his diet to avoid allergic reactions and prescribe medications in case of an allergic reaction. In addition, a consultation with a nutritionist can be helpful to plan a nutritious diet and learn how to avoid exposure to citrus products. You should avoid oranges, tangerines, grapefruit, lemons, limes, mandarins, tangelos and pomelos, as well as juices from these fruits.

Be sure to read food labels (e.g., on baked goods, premixed cereals, flavored drinks, tea, candy, medicines) to avoid foods with orange or lemon extract or peels. Ask the allergist for a more complete list of foods and additives to avoid. Make sure your son still gets enough Vitamin C by eating other fruits such as papaya, mango, watermelon, cantaloupe and blueberries as well as vegetables such as green and red peppers, potatoes, broccoli and spinach. Since strawberries and tomatoes are not related to citrus fruits, it would be unlikely that your son would also be allergic to them. True allergies to strawberries and tomatoes are rare. But strawberries and tomatoes are both acidic and can lead to irritation reactions. So if your son had a non-allergic or irritation reaction to the citrus fruits, he could also have an irritation reaction to the acids in strawberries and tomatoes.

For more information, visit the Food Allergy and Anaphylaxis Network www.foodallergy.org